Resource selection for device to device discovery or communication

ABSTRACT

Systems, methods, and instrumentalities are disclosed to manage interference caused by D2D communications. A wireless transmit receive unit (WTRU) may include a processor. The processor may be configured to perform one or more of the following. The processor may determine to send information using a device-to-device transmission via a resource pool from a plurality of resource pools. Each resource pool may be associated with a range of reference signal receive power (RSRP) values. The processor may determine a RSRP measurement of a cell associated with the WTRU. The processor may select a resource pool from the plurality of resource pools based on the RSRP measurement of the cell. The RSRP measurement of the cell may be within the range of RSRP values associated with the selected resource pool. The processor may send the information using the selected resource pool.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/933,238, filed Jan. 29, 2014, U.S. Provisional Application No.61/955,746, filed Mar. 19, 2014, U.S. Provisional Application No.61/990,046, filed May 7, 2014, and U.S. Provisional Application No.62/075,768, filed Nov. 5, 2014, the disclosures of which areincorporated herein by reference in their entirety.

BACKGROUND

The proximity between devices may be determined using LTE positioning.In Device-to-Device (D2D) neighbor discovery, two or more devices maydetermine their relative proximity based on direct radio communications.Additional interference may be introduced by these D2D transmissions.

SUMMARY

Systems, methods, and instrumentalities are disclosed to managepotential interference that may be caused by D2D communications. A firstWTRU may send a resource report to a network. The first WTRU may receiveone or more resources from the network for transmission of a discoverysignal. The first WTRU may send the discovery signal to a second WTRU.

The resource report may include one or more of resources fortransmission for D2D communication, identity of a discovery process,location information, outcome of a discovery process, outcome of atransmission attempt, measured resource utilization, network resourceconfiguration information, and/or a number of failures or successes on aresource.

The resource report may be sent by the first WTRU based on aconfiguration of a WTRU (e.g., the first WTRU and/or the second WTRU), aperiodic schedule, an aperiodic schedule, a change in operation status,an outcome of a discovery process, an outcome of a discovery signaldecoded by the second WTRU, and/or an outcome of a transmission attemptby the first WTRU.

The one or more resources may be characterized by one or more of timinginformation, frequency information, sequence information, and a hoppingpattern.

The first WTRU and the second WTRU may be served by the same networkelement (e.g., eNB). The first WTRU may be served by a first eNB and thesecond WTRU may be served by a second eNB. The first WTRU may be servedby an eNB and the second WTRU may be out-of-coverage of the network. Thefirst WTRU may be out-of-coverage of the network and the second WTRU maybe served by an eNB.

A wireless transmit receive unit (WTRU) may include a processor. Theprocessor may be configured to perform one or more of the following. Theprocessor may determine to send information using a device-to-devicetransmission via a resource pool from a plurality of resource pools.Each resource pool may be associated with a range of reference signalreceive power (RSRP) values. The processor may determine a RSRPmeasurement of a cell associated with the WTRU. The processor may selecta resource pool from the plurality of resource pools based on the RSRPmeasurement of the cell. The RSRP measurement of the cell may be withinthe range of RSRP values associated with the selected resource pool. Theprocessor may send the information using the selected resource pool.

The range of RRSP values associated with the selected resource pool mayinclude a low RSRP threshold and a high RSRP threshold. The RSRPmeasurement of the cell may be between the low RSRP threshold and thehigh RSRP threshold.

The processor may be further configured to select a resource from aplurality of resources in the selected resource pool. The processor maybe configured to select the resource using a randomization function or apseudo-random function. The processor may be configured to send theinformation on the selected resource. The selected resource may includeone or more subframes. The selected resource may include one or morephysical resource blocks (PRBs).

The processor may be further configured to receive a configuration viaradio resource control (RRC) signaling and determine, based on theconfiguration, that the selection of the resource pool is based on RSRP.The configuration may identify the resource pool and the range of RSRPvalues associated with the resource pool.

A method (e.g., a computer-implemented method) may include determining(e.g., at a processor) to send information using a device-to-devicetransmission via a resource pool from a plurality of resource pools.Each resource pool may be associated with a range of reference signalreceive power (RSRP) values. The method may include determining (e.g.,via a processor) a RSRP measurement of a cell associated with the WTRU.The method may include selecting (e.g., by a processor) a resource poolfrom the plurality of resource pools based on the RSRP measurement ofthe cell. The RSRP measurement of the cell may be within the range ofRSRP values associated with the selected resource pool. The method mayinclude sending (e.g., via a transmitter) the information using theselected resource pool.

The range of RRSP values associated with the selected resource pool mayinclude a low RSRP threshold and a high RSRP threshold. The RSRPmeasurement may be between the low RSRP threshold and the high RSRPthreshold.

The method may include selecting a resource from a plurality ofresources in the selected resource pool. The method may includeselecting the resource using a randomization function or a pseudo-randomfunction. The method may include sending the information on the selectedresource.

The method may include determining that the device-to-devicetransmission is a Type 1 device-to-device transmission. The Type 1device-to-device transmission may be characterized by a WTRU selectingthe resource pool from the plurality of resource pools. The Type 1device-to-device transmission may be characterized by a WTRU selecting aresource from a plurality of resources in the selected resource pool.The method may include receiving a request to send the information usingthe device-to-device transmission and determining to send theinformation using the device-to-device transmission in response to therequest.

A wireless transmit receive unit (WTRU) may include a processor. Theprocessor may be configured for one or more of the following. Theprocessor may receive a device-to-device transmission request to sendinformation via a resource pool from a plurality of resource pools. Theprocessor may determine that selection of the resource pool from theplurality of resource pools is based on reference signal receive power(RSRP). The processor may receive a RSRP threshold associated with atleast one resource pool from the plurality of resource pools. Theprocessor may determine a RSRP measurement of a base station. Theprocessor may compare the RSRP measurement of the base station with theRSRP threshold associated with the at least one resource pool. Theprocessor may select the at least one resource pool to send theinformation via device-to-device transmission when the RSRP measurementof the base station is above the RSRP threshold. The processor may sendthe information using the at least one resource pool when the at leastone resource pool is selected to send the information.

The selected resource pool may include a plurality of resources. Theprocessor may select a resource from the plurality of resources based ona randomization function and send the information using the selectedresource. The resource may include a subframe or a physical resourceblock (PRB). The processor may receive a system information block (SIB)that identifies the at least one resource pool and indicates the RSRPthreshold associated with the at least one resource pool. The RSRPthreshold may be a low RSRP threshold of an open-ended range of RSRPvalues or a high RSRP threshold of the open-ended range of RSRP values.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A.

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A.

FIG. 1D is a system diagram of another example radio access network andanother example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1E is a system diagram of another example radio access network andanother example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 2 is a diagram of an example of intra-cell interference between D2Dlinks.

FIG. 3 is a diagram of an example of inter-cell interference between D2Dlinks and from a D2D link to a cellular link.

FIG. 4 is a diagram of an example of intra-cell interference from acellular link to D2D links.

FIG. 5 is a diagram of an example of a discovery occasion.

FIG. 6 is a diagram of an example of scenarios for in-coverage,out-of-coverage, and partial coverage D2D discovery and/orcommunications.

FIG. 7 is a diagram of an example scenario of communication between anin-coverage WTRU and an out-of-coverage WTRU.

FIG. 8 is a diagram of an example of signaling that may be used for anout-of-coverage WTRU to determine and/or drive resource allocation.

FIG. 9 is a diagram of an example of signaling that may be used for aneNB and/or an in-coverage WTRU to determine and/or drive resourceallocation.

FIG. 10 is a diagram of an example of resource allocation of discoveryresources across two eNBs, eNB A and eNB B.

DETAILED DESCRIPTION

A detailed description of illustrative embodiments will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be exemplary and in no way limitthe scope of the application.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, and/or 102 d (whichgenerally or collectively may be referred to as WTRU 102), a radioaccess network (RAN) 103/104/105, a core network 106/107/109, a publicswitched telephone network (PSTN) 108, the Internet 110, and othernetworks 112, though it will be appreciated that the disclosedembodiments contemplate any number of WTRUs, base stations, networks,and/or network elements. Each of the WTRUs 102 a, 102 b, 102 c, 102 dmay be any type of device configured to operate and/or communicate in awireless environment. By way of example, the WTRUs 102 a, 102 b, 102 c,102 d may be configured to transmit and/or receive wireless signals andmay include user equipment (WTRU), a mobile station, a fixed or mobilesubscriber unit, a pager, a cellular telephone, a personal digitalassistant (PDA), a smartphone, a laptop, a netbook, a personal computer,a wireless sensor, consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106/107/109, theInternet 110, and/or the networks 112. By way of example, the basestations 114 a, 114 b may be a base transceiver station (BTS), a Node-B,an eNode B, a Home Node B, a Home eNode B, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),such as a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 a and/or the base station114 b may be configured to transmit and/or receive wireless signalswithin a particular geographic region, which may be referred to as acell (not shown). The cell may further be divided into cell sectors. Forexample, the cell associated with the base station 114 a may be dividedinto three sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, e.g., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 115/116/117,which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, etc.). The air interface 115/116/117 may be established using anysuitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 103/104/105 and the WTRUs 102a, 102 b, 102 c may implement a radio technology such as UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA),which may establish the air interface 115/116/117 using wideband CDMA(WCDMA). WCDMA may include communication protocols such as High-SpeedPacket Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may includeHigh-Speed Downlink Packet Access (HSDPA) and/or High-Speed UplinkPacket Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface115/116/117 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (e.g.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106/107/109.

The RAN 103/104/105 may be in communication with the core network106/107/109, which may be any type of network configured to providevoice, data, applications, and/or voice over internet protocol (VoIP)services to one or more of the WTRUs 102 a, 102 b, 102 c, 102 d. Forexample, the core network 106/107/109 may provide call control, billingservices, mobile location-based services, pre-paid calling, Internetconnectivity, video distribution, etc., and/or perform high-levelsecurity functions, such as user authentication. Although not shown inFIG. 1A, it will be appreciated that the RAN 103/104/105 and/or the corenetwork 106/107/109 may be in direct or indirect communication withother RANs that employ the same RAT as the RAN 103/104/105 or adifferent RAT. For example, in addition to being connected to the RAN103/104/105, which may be utilizing an E-UTRA radio technology, the corenetwork 106/107/109 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, such asthe transmission control protocol (TCP), user datagram protocol (UDP)and the internet protocol (IP) in the TCP/IP internet protocol suite.The networks 112 may include wired or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment. Also, embodiments contemplate that thebase stations 114 a and 114 b, and/or the nodes that base stations 114 aand 114 b may represent, such as but not limited to transceiver station(BTS), a Node-B, a site controller, an access point (AP), a home node-B,an evolved home node-B (eNodeB), a home evolved node-B (HeNB), a homeevolved node-B gateway, and proxy nodes, among others, may include someor all of the elements depicted in FIG. 1B and described herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in one embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. In another embodiment, thetransmit/receive element 122 may be an emitter/detector configured totransmit and/or receive IR, UV, or visible light signals, for example.In yet another embodiment, the transmit/receive element 122 may beconfigured to transmit and receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 115/116/117.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 115. The RAN 103 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 103 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 115. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 1D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, 160 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, 160 c in the RAN 104 via the S1 interface. The serving gateway164 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 164 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 117. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 1E, the RAN 105 may include base stations 180 a, 180 b,180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell (not shown) in theRAN 105 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 117. In oneembodiment, the base stations 180 a, 180 b, 180 c may implement MIMOtechnology. Thus, the base station 180 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 180 a, 180 b, 180 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 109.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 109 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,180 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 180 a, 180 b,180 c and the ASN gateway 182 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements aredepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 186 may be responsible for userauthentication and for supporting user services. The gateway 188 mayfacilitate interworking with other networks. For example, the gateway188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

FIG. 2 is a diagram of an example of intra-cell interference between D2Dlinks. When two or more D2D transmitting WTRUs in the same cell transmitsignals (e.g., discovery signals) on the same resource, interference202, 204 may be introduced to the D2D transmission in the cell.

FIG. 3 is a diagram of an example of inter-cell interference between D2Dlinks and from a D2D link to a cellular link. When a cell edge D2Dtransmitting WTRU transmits a signal (e.g., a discovery signal) usingthe same resources as one or more transmitting WTRUs (e.g., a WTRUtransmitting a D2D signal, a cellular signal (e.g., such as an ULPUSCH), and/or the like in a neighbor cell, interference 302 may beintroduced to a signal, such as a D2D signal 304 and/or a PUSCHtransmission 306, in a neighbor cell.

FIG. 4 is a diagram of an example of intra-cell interference from acellular link to one or more D2D links. When a cell edge cellulartransmitting WTRU transmits a signal (e.g., an UL PUSCH transmission)using the same resources as a D2D transmitting WTRU in a neighbor cell,interference 402 may be introduced to D2D transmissions in the neighborcell.

The interference between cellular UL transmission and D2D links may beavoided by dedicating a number of subframes to D2D. The interferencebetween D2D links within the same cell as well as cross neighbor cellsmay be managed.

Interference may be managed by means of resource allocation. Forexample, by allocating resources properly, the probability that two ormore D2D WTRUs select the same resource may be reduced. For example, thenetwork may determine the amount of resources to allocate to two or moreD2D transmitting WTRUs. For example, the network may determine whichresources to allocate to which WTRU. For example, D2D WTRU may selectthe resources to transmit a discovery signal.

FIG. 5 is a diagram illustrating an example of a discovery occasion. Adiscovery occasion may refer to a number of consecutive subframes thatmay be reserved in a discovery period. The discovery occasion may beused for discovery. The discovery period may refer to a period of timebetween the start of two consecutive discovery occasions. For example,the discovery period may be t seconds. The discovery occasion cycle mayrefer to a set of Ndo>1 consecutive discovery occasions.

Network may refer to a node (e.g., any node) that is involved in thecontrol of the allocation of resources for a discovery signaltransmission. For example, the network may refer to an eNB, a ProSeserver, mobile device that may act as a centralized coordinating entityfor the D2D discovery function, and/or the like. One or more embodimentsprovided herein may be provided in the context of discovery. One or moreembodiments provided herein may apply to a direct device-to-device (D2D)communication. One or more embodiments provided herein may be applicableto the data part of a D2D communication. One or more embodimentsprovided herein may be applicable to the control part of a D2Dcommunication (e.g., the SA, D2DSS, or other control signal). Forexample, one or more embodiments provided herein may be applicable toSidelink Control Information (SCI) that may be carried on the PhysicalSidelink Control Channel (PSCCH) or to Sidelink Synchronization Signalsthat may be carried on the Physical Sidelink Broadcast Channel (PSBCH).

A transmitter WTRU may transmit a Scheduling Assignment (SA) that mayindicate, for example, resources (e.g., time and frequency, for examplesubframe(s) and/or PRB(s)) used for transmission of D2D data to areceiver WTRU, such as when WTRUs may be performing D2D communications.For example, a transmitter WTRU may transmit D2D data in resources thatmay be indicated by a Scheduling Assignment. A receiving WTRU maydetermine resources (e.g., time and frequency) to receive data based on,for example, the reception of a Scheduling Assignment.

A D2DSS may be a device-to-device synchronization signal.

A WTRU may be configured with one or more independent discoveryprocesses. For example, a discovery process may be tied to a specificapplication and/or may correspond to a specific discovery signal thatthe WTRU transmits and/or receives. Examples provided herein may bediscovery process-specific and/or be applicable to all discoveryprocesses, e.g., at once. A WTRU may be configured with one or more D2Dcommunications processes. One or more embodiments described herein maybe applicable on a per-D2D communication process basis. One or moreembodiments described herein may be applicable to a plurality of (e.g.,all) D2D communications processes, for example, at once. One or moreembodiments described herein may be applicable to certain D2D modes ofoperation (e.g., Mode 1—eNB-controlled, Mode 2—distributed, etc.) and/orto certain D2D coverage states (e.g., in-coverage, edge-of-coverage,out-of-coverage).

A discovery signal may correspond to a D2D message that carriesinformation pertaining to, for example, a discovery process (e.g.,proximity, discovery identities). A D2D message may carry, for example,a data part of D2D communications. A D2D message may carry, for example,Scheduling Assignment information that may be used to perform a function(e.g., scheduling the data part of D2D communications).

One or more embodiments described herein in the context of discoverysignals may be applicable to any D2D transmissions and/or messages.Discovery signal, discovery signal resource, measurements, etc. may beused interchangeably and/or applied to a D2D message, D2D resources, ormeasurement.

One or more embodiments for resource allocation may be provided. A WTRUmay be allocated one or more resources for the transmission of adiscovery signal. A WTRU may be allocated one or more resources for D2Dtransmissions (e.g., SA and/or data transmissions). A WTRU may selectone or more resources for D2D transmissions (e.g., SA and/or datatransmissions). Resource allocation may be characterized by timinginformation (e.g. when is the resource available, at the granularity ofone transmission time interval (TTI) and/or subframe), by frequency(e.g. carrier, set of PRBs (physical resource blocks), and/or the like),by information (e.g. where in frequency is the resource located, e.g.for one or more subframes), by parameters that may determine how thesignal is transmitted and/or received (e.g. sequence, hopping pattern,and/or the like), and/or the like. Timing information may includeabsolute timing information, periodic allocation information, timinginformation relative to another aspect of the discovery configurationand/or process, and/or the like. Information relating to resourceallocation may be signaled (e.g., explicitly signaled) and/orparameterized, for example, such that the WTRU may implicitly calculateand/or determine the resource allocation (e.g., in time and/or infrequency) and/or the WTRU may be tabulated such that indices to one ormore entries in a table(s) may be exchanged.

The resource allocation may be structured, for example, such that it maybe represented as an indexed list of elements, for example, where eachelement may correspond to a specific resource. For example, a WTRU maybe configured with a configuration index which may represent one of anumber X possible configurations for the specific applicable framestructure (e.g., FDD or TDD when under network coverage, a framestructure specific to a direct WTRU-to-WTRU communication, and/ordiscovery operation). The configuration index may refer to a tabulatedvalue which may be used by the WTRU to determine the set of resourcesavailable (e.g., in the cell). The WTRU may use this information todetermine the indexing of the resources.

The WTRU may be configured with a frequency offset (e.g., if theresources span a subset of all the physical resource blocks (PRBs) in agiven subframe). The frequency offset may indicate the first PRB of theresource for a given subframe. For a time interval (e.g., a 10 ms frame,a time period of Y TTIs, Y ms, and/or Y radio frames, etc.), the WTRUmay determine what subframe includes a resource and/or the location ofthe first PRB of the resource. The resource may be indexed for a period(e.g., period Y) in increasing order of the subframe number and/or ofthe PRB in the frequency domain (e.g., if multiple resources may bemultiplexed in frequency for a given subframe). For example, the firstresource in a period Y may be allocated index 0, the second resource inthe period Y may be allocated index 1, and so on. The WTRU may beallocated resources such that all resources in the set are availableand/or such that a subset of resources in the set may be available, forexample, by receiving (e.g., as part of the configuration) a maskingparameter and/or specific indices that represent the subset of resourceswithin the set of resources.

A resource for SA and/or its associated data transmission may comprisean index to a plurality of frequency and/or PRB elements, for example,in D2D communications. A WTRU may be configured to repeat SA. A SAresource may comprise, for example, an associated transmission patternindicating information (e.g., frequency and/or time location of a SAover a period of time). A scheduling period may refer to the frequencyand/or time location of a SA over a period of time. A resource for datatransmission may comprise an associated transmission pattern. Data maynot necessarily repeat. Data may comprise transmission opportunities fora WTRU.

For example, a WTRU may be configured with one or more resources for D2Dcommunications. One or more resources for D2D communications may beassociated with a mode of operation (e.g., Mode 1, Mode 2, etc.). One ormore resources for D2D communications may be associated with a coveragestate. For example, a WTRU may be configured to report to an eNB forresources that may be in control of an eNB, e.g., for a resource poolassociated to operations (e.g., in-coverage, edge-of-coverageoperations).

WTRU measurement and reporting may be provided. The WTRU may perform oneor more measurements and report the one or more measurements to thenetwork (e.g., eNB), for example, to help the network determine theamount of resources to allocate to the WTRU.

An availability status of a resource may be determined based on ameasured energy level. The measured energy level may be compared with athreshold to determine the availability status of the resource.

A resource may be determined to be occupied and/or unavailable fortransmission. For example, a resource may be determined to be occupiedand/or unavailable for transmission when a measured energy level on theresource is above a threshold. The resource may be unavailable when ameasured energy level on a resource is above a threshold for apredefined period of time. The resource may be unavailable when the WTRUdetermines that the resource is being used by another WTRU, for example,by means of a received and/or detected announcement message and/orcontrol message, and/or the like.

A resource may be determined to be available for transmission. Forexample, a resource may be determined to be available for transmissionwhen a measured energy level is below a threshold. The resource may beavailable when a measured energy level is below a threshold for apredefined period of time. A resource that is available may be used bythe WTRU at any time (e.g., if allocated by the network for that WTRU totransmit), and/or the like.

A discovery signal may be determined to be present on a resource. Acommunication signal may be determined to be present on a resource. Forexample, a signal (e.g., discovery signal and/or communication signal)may be determined to be present on a resource when a measured energy onthe resource is above a defined threshold. For example, the signal maybe detected on the resource when a measured energy on the resource isabove a threshold for a period of time. The signal may be detected onthe resource when a discovery signal is decoded successfully on theresource. The signal may be detected on the resource when a controlsignal associated with a discovery signal and/or communication signal(e.g., indicating the presence of the discovery signal or communicationsignal) is decoded successfully, and/or the like.

A WTRU may measure SA utilization by counting SAs (e.g., successfullyreceived SAs) in a time frame. A determination may be made that SAresources have been successfully received, for example, if a WTRUdecodes a SA and associated CRC checks. A SA may be consideredsuccessfully received if the measured SNR is above a threshold. Thethreshold may be determined (e.g., by tests, configured, etc.). The WTRUmay count SAs when the CRC is masked by an identity that is unknown to aWTRU. An SA resource that is successfully received may be consideredutilized.

A WTRU may measure SA utilization by measuring energy in SA resources.An SA resource may be considered utilized, for example, if a WTRUmeasures the energy level in an SA resource location (e.g., intime/frequency). An SA resource may be considered utilized if a WTRUdetermines that the energy level in an SA resource is above a threshold.A threshold may be predefined. A threshold may be defined by otherparameters (e.g., by tests or configured).

A WTRU may measure near-far effect. A WTRU may determine near-fareffect. Near-far effect may impact, for example, the ability of a WTRUto receive communications from other WTRUs (e.g., when the signalstrength of a WTRU may be stronger than the signal of other WTRUs, whendetection of a low received power signal is more difficult than normal,and/or the like).

A WTRU may suffer from the near-far effect, for example, when a WTRUreceives signal from one or more WTRUs with a stronger power than otherWTRU signals. A WTRU may be configured to detect examples of near-fareffect by measuring the signal power of one or more devices in thevicinity. A WTRU may be configured to detect examples of near-far effectby determining whether one or more signals in the vicinity has thepotential to create near-far effect. A WTRU may be configured to detectexamples of near-far effect by determining when one or more signals arestronger than other signals by an amount, such as, for example, apredefined amount or threshold.

A WTRU may determine D2D data resources based on, for example, D2D datatransmission patterns. A D2D data resource may comprise a predefinedpattern (e.g., in time, in frequency, or both). A WTRU may be configuredto measure for a D2D data pattern. A WTRU may be configured to measurefor an aggregate D2D data pattern (e.g., a WTRU may be configured toreport for all PRBs for a specific time-based pattern).

The measure energy level may be weighted (e.g., divided, subtracted inthe dB domain, modified, and/or the like) by a thermal noisemeasurement/estimate performed by the WTRU.

A WTRU may report the resource usage to the network. A WTRU may performtransmissions, such as when a WTRU is configured with resources fortransmission (e.g., of a discovery signal, a D2D transmission, or a D2Dmessage). If the resource is dedicated to a WTRU and/or discoveryprocess, the outcome (e.g., of the discovery or D2D transmissions) maybe less likely impacted by interference from other transmitting WTRUs.In this case, it may be assumed that there is no other WTRU in proximityof the transmitting WTRU if no other WTRU successfully receive thediscovery signal from the transmitting WTRU.

If the resource may be shared by a plurality of transmitting WTRUs(e.g., for the same or for different discovery processes and/or D2Dtransmissions), the outcome of the discovery may be impacted byinterference from other transmitting WTRUs that may contend for theresource and/or that may be within proximity of each other. In suchcase, it may not be possible to determine whether a monitoring WTRU hasnot been successful in receiving the discovery signal or D2D message,for example, because the received signal may be too weak (e.g., themonitoring WTRU may not be within proximity of the transmitting WTRU),because the level of interference is too high (e.g. the monitoring WTRUmay be within proximity of the transmitting WTRU but the signal may notbe detected with sufficient signal to noise ratio), and/or the like.This may be problematic for the network resource management, forexample, because there may not be means to determine if more resourcesare needed for discovery/communications.

Collisions may occur in a resource that is shared by different WTRUsand/or by the discovery processes. The network may allocate one or moreresources to a plurality of transmitting WTRUs. A collision may occurfor a concerned resource when more than one transmitting WTRUs aretransmitting a discovery signal. A collision may occur for a concernedresource when a plurality of transmitting WTRUs are transmitting a D2Dmessage. The level of interference generated may be a function of thedistance between the transmitting WTRUs that generate the collision onthe concerned resource and/or as a function of the relative distance ofa receiving WTRU to such transmitting WTRUs (e.g., when the signal powerreceived from the WTRUs has a ratio that trends towards 1). The networkmay allocate resources by estimating the rate of discovery events. Thenetwork may allocate resources by estimating the rate of D2Dtransmission events. The network may allocate resources by estimatingthe rate of transmission by WTRUs sharing the resource. The network mayallocate resources by targeting a specific collision rate, for example,such that the network does not over-allocate the resources (e.g., lowcollision rate, sub-optimal use of resources, etc.) and/orunder-allocate the resources (e.g., high collision rate, lowerefficiency of the discovery mechanism, etc.).

The network may not determine the proper operating point when allocatingresources. For example, the network may not know the frequency oftransmission of the discovery signals (e.g., in case of WTRU-autonomoustriggers), the number of active transmitting WTRUs (e.g., in casediscovery transmission is supported in IDLE mode), the geographicaldistribution of the WTRUs (e.g., transmitting or receiving) involved inD2D transmissions (e.g., discovery process(es) or data relatedtransmissions, such as SA and/or data) in a given cell for whichresources are allocated, and/or the like.

The network may redistribute the load and/or minimize collisions risk.The network may monitor resource usage for a transmission(s) (e.g., D2Dtransmission, discovery signal, data related transmission, and/or thelike) in shared resources, for example, such that the network mayre-allocate resources when high collision rates are detected. When thenetwork may determine that collisions are below a certain threshold, thenetwork may determine that the outcome of the discovery process is afunction of the proximity between WTRUs, for example, given thatinterference may be deemed to be at an acceptable level for theallocated resources.

The WTRU may identify one or more of the resources used for transmissionusing indices. A reporting mechanism may include resource usage.Resource usage may include information related to past transmissions ofa discovery signal for a given resource allocation. For example,resource usage may include information related to planned and/orscheduled transmission of a discovery signal and/or transmissions of adiscovery signal that happened in a past configured time period.Reporting may be assembled by a transmitting WTRU. Reporting may bereceived by a network node, for example, a node from which the WTRU hasreceived the configuration for the resource allocation for transmissionof discovery signals. Reporting (e.g., which may include format,triggers, time windows, and/or the like) may be configured, for example,together with the resource allocation.

The network node (e.g., a base station such as an eNB) may configure oneor more transmitting WTRUs that are configured with similar resourceallocation for reporting. When the network node receives one or morereports, the network node may use the received information to derivecollision probability for a resource. The network node may determinewhether or not such probability is above a threshold. If above a certainthreshold, the network may initiate a reconfiguration for one or moreWTRUs, for example, such that the discovery signals are better spreadacross the allocated resources in the cell.

WTRUs may be in proximity of each other but the interference levels(e.g., which may be due to collisions within the resource used for thediscovery signal) may impair other WTRUs from properly receiving thediscovery signal. The WTRUs and/or the network may determine whetheranother WTRU did not discover the WTRU, for example, because the WTRU isnot in proximity and/or because of the collisions.

A D2D discovery may be a Type 1 D2D discovery where a WTRU may select aresource. A D2D discovery may be a Type 2 discovery where a networkelement may select a resource for a WTRU. A D2D communication may be aMode 1 D2D communication where a network elements may control resourceand/or transmission parameters for a WTRU. Mode 1 D2D communication maybe used when the WTRU is in coverage. A D2D communication may be a Mode2 D2D communication where a WTRU may determine resources(s) and/ortransmission parameter(s). Type 1 D2D discovery may be similar to Mode 2D2D communication.

D2D communication transmission may take place under network coverage oroutside of network coverage. A WTRU may be configured to operate withoutnetwork control (e.g., in Mode 2 D2D communication), for example, whileWTRU communications under network coverage may be controlled by anetwork base station and/or an eNB (e.g., Mode 1). A WTRU may selectresources for transmissions autonomously when, for example, WTRUcommunications take place outside of the network coverage. The networkmay be unaware of potential high interference situations. The networkmay be made aware of the D2D resources utilization, for example, so thatresources may be available for D2D communications.

Collisions of the SA and/or data may occur when outside of networkcoverage. Collisions of the SA and/or data may occur between a WTRUcontrolled by an eNB and another WTRU outside network coverage.

The network may re-use (e.g., allocate) the same resource to one or moreWTRUs when, for example, under network coverage. WTRUs may be inproximity when a network may not be aware of the geographical locationof some WTRUs. The transmissions may collide on the same resources.

The report may include one or more of the following. The report mayinclude the identity of resources (e.g. the concerned resources), theidentity of the discover process and/or event, location information, theoutcome of a discovery process and/or event, the outcome of one or moretransmission events, measured resource utilization, whether networkresource configuration may be insufficient, a report by a monitoringWTRU on the outcome of discovery signal decoding, and/or the like.

A concerned resource may refer to a resource used for transmissions ofdirect WTRU-to-WTRU signals, for example, a discovery signaltransmission, SA, data pattern index, and/or the like. For example, thereport may include one or more indices describing one or more of theresources (e.g., in time/frequency, for example subframe(s) or PRB(s)),which may be used for transmission.

A reported resource may be associated with one or more of the following.For example, a reported resource may indicate the resource for which theWTRU has performed a transmission. For example, the reported resourcemay indicate a resource for which the WTRU has performed a transmissionwithin a period, for example, the last Z resource allocation period(e.g., a frame, a period represented by Y TTIs, Y ms, and/or Y frames).The period may be configurable. The report may be sent by a transmittingWTRU.

For example, a reported resource may indicate a resource for which theWTRU may be expected to perform a transmission, for example, atransmission that may not have been performed at the time the WTRUassembles (e.g., generates) the report. For example, the reportedresource may indicate a resource for which the WTRU may be expected toperform a transmission for a period, for example, the next Z resourceallocation period (e.g., a frame, a period represented by Y TTIs, Y ms,and/or Y frames). The period may be configurable. The report may be sentby a transmitting WTRU.

For example, a reported resource may indicate an index of a resource forwhich the WTRU has measured the largest amount of energy (e.g., one ormore). For example, a reported resource may indicate an index of aresource for which the WTRU has measured the largest amount of energywithin a period, for example, the last Z resource allocation period(e.g., a frame, a period represented by Y TTIs, Y ms, and/or Y frames).The period may be configurable. If multiple resources are reported, thesignaling format may include means for the receiver to determine thenumber of elements in the report, for example, by including the totalnumber of elements in the report. The report may be sent by a monitoringWTRU and/or by a transmitting WTRU. For example, a reported resource mayindicate an index of a resource for which collision has been detected.

For example, a reported resource may indicate an index of the resourceor index of patterns for which a transmission failed (e.g., noacknowledgment(s) where received or a percentage of the transmissionswere not acknowledged)

For example, a reported resource may indicate an index of a resource forwhich a near-far effect has been detected.

For example, the WTRU may report an index corresponding to a set ofresources and/or a process identity (e.g., an entity receiving thereport may determine the concerned set of resources) followed by zero(e.g., if no transmission has occurred for the reporting period). TheWTRU may report one or more indices each corresponding to a resource inwhich the WTRU has performed a transmission and/or is expected to haveperformed a transmission. A report may include the identity of thediscovery process and/or event. An identity may be associated with aconcerned resource and/or may identify (e.g., implicitly identify) aconcerned resource. A monitoring WTRU may report the ID of atransmitting WTRU with a discovery signal that has been successfullydecoded on a resource and/or a set of resources (e.g., identificationmay correspond to the ProSe ID decoded on the discovery resource). AWTRU may report the ID of one or more transmitting WTRUs, for example,when near-far effect causes issues (i.e. when received power is strong,when received power is faint). A WTRU may report the ID carried on theSA of interest. A WTRU may report the ID carried on the SA associated tothe D2D data transmission for which the WTRU is reporting.

A report may include location information. Location information may beassociated with a discovery signal transmission, a discovery signalreception, and/or the report. A WTRU (e.g., a transmitting WTRU and/or areceiving WTRU) may determine its location, for example, based on thecell ID, GPS information, and/or other location information. The WTRUmay include the location information in the report.

A report may include an outcome of a concerned discovery process and/orevent. If the WTRU has means to determine whether or not a discoveryprocess and/or event has been successful, the WTRU may report theoutcome for the concerned resource, discovery process, and/or event. Forexample, a WTRU may determine that the outcome is successful for adiscovery process and/or event that may be multidirectional. Amultidirectional discovery process and/or event may be from thereception and/or detection of a discovery signal from another WTRU, forexample, as a response to its own transmission. A multidirectionaldiscovery process and/or event may be from the establishment of a directcommunication channel with one or more WTRUs subsequent to thetransmission of the discovery signal for the concerned resource(s)and/or for the concerned discovery process and/or event.

A report may include the outcome of at least a transmission attempt. Atransmitting WTRU may report a failure to transmit a D2D or discoverymessage (e.g., due to no and/or limited available resources for a WTRUto transmit a discovery signal, for example, for a defined period oftime, and/or due to a collision on a resource with another transmission.

A report may include the outcome based on resource availability. TheWTRU may determine that insufficient resources are available fortransmission (e.g., of discovery signal, SA or D2D data) according toone or a combination of the following.

The WTRU may determine that insufficient resources are available fortransmission when the measured received energy on one or more of theresources (e.g., all resources) are above a certain threshold. Resourcesmay be considered to be occupied by other WTRUs.

The WTRU may determine that insufficient resources are available fortransmission when the WTRU determines other WTRUs are using one or moreof the resources (e.g., all resources), for example, which may bedetermined by means of receiving announcement messages (e.g., SA) and/orother messages indicating which resources are being used. There may beno resource available for the WTRU to transmit, for example, a discoverysignal, SA or D2D data.

The WTRU may determine that insufficient resources are available fortransmission when the network is not allocating any resource for a D2DWTRU, for example, within a time period.

The WTRU may determine that insufficient resources are available fortransmission. The WTRU may determine the number of resource available isinsufficient (e.g., for the WTRU to meet the required and/or targetdiscovery QoS, transmission rate, and/or D2D data) for example, based onthe received energy measured on the resources, a certain threshold,and/or based on the received SA, This may be determined, for example,for a period of time.

The transmitting WTRU may report after one or more successfultransmissions. A successful transmission may include the WTRU findingavailable resource(s) to transmit a discovery signal. The WTRU mayreport one or more of the following information associated with asuccessful transmission.

The WTRU may report the number of transmission attempts before the WTRUcan successfully perform a transmission of, for example, a discoverysignal, D2D transmissions, D2D data, and/or SA (e.g., the number ofsub-frames in which no resources were available). A transmission attemptmay include one or more discovery subframes in which the WTRU attemptsto transmit a D2D transmission, for example, over the air on an alloweddiscovery resource. For example, the WTRU may determine that an attempthas failed if the WTRU is allowed to transmit on the D2D resource(s) butdoes not find an available resource (e.g., the measured energy on theresource is above a threshold) for one or more subframes.

The WTRU may report the average time it takes to successfully transmit adiscovery signal, for example, which may be determined to be the time itis available for transmission to the time it takes to transmit it overthe air. The average time may be determined over a number of discoverysignal transmissions, over a number of discovery periods, and/or withina single period. The WTRU may report the ratio of attempts to success.The WTRU may report the amount of D2D data. The WTRU may report thenumber of D2D data transmissions carried out by the WTRU (e.g., in termsof MAC PDUs, total data delivered, data rate, etc.).

The transmitting WTRU may send the report after determining that it hasinsufficient resources to meet its target QoS and/or discoverytransmission rate, for example, for a configured amount of time. TheWTRU may report resource availability, resource utilization, and/or theamount of resources used by the WTRU to meet its target QoS and/ordiscovery transmission rate, for example, as determined per the WTRUdiscovery processes and/or D2D data configuration.

The report may include the outcome based on transmissionacknowledgement. A WTRU may have means to determine whether atransmission or a plurality of transmissions within a time period weresuccessful by, for example, reception of acknowledgment of transmittedPDU (e.g. HARQ, RLC, TCP/IP ACK, etc.). A WTRU may determine that a PDUor a plurality of PDUs within a time period were not delivered, forexample, due to lack of acknowledgment for those PDUs, or lack of aresponse from the receiving WTRU. For example, a WTRU may consider atransmission successful if a PDU was acknowledged. A WTRU may consider atransmission unsuccessful if, for example, a PDU exceeds itsretransmission attempts without receiving an ACK. A WTRU may reportfailure to transmit on a given resource, a plurality of configuredresources for reporting, or a resource plurality (e.g., a pattern)within a time. A WTRU may report number of failures or successes overtotal transmission opportunities/attempts in a time period. A WTRU mayreport percentage of failures over transmission opportunities. A WTRUmay report success rate or failure rates on a resource. A WTRU mayreport a plurality of configured resources for reporting. A WTRU mayreport a resource plurality (e.g., pattern) measured within a time. AWTRU may report an index of the resource, resource plurality or patternused for the transmission in which failure to transmit may have beendetected. A WTRU may report TTIs in which failure may have beendetected.

The report may include the measured resource utilization. Thetransmitting and/or monitoring WTRU may report the measured resourceutilization while attempting to transmit and/or receive a discoverysignal, for example, over a period of time regardless of whether it isattempting to transmit or not. The resources a WTRU is measuring may beconfigured by the network. A WTRU may determine the resources to measurebased on, for example, the available resources for D2D transmissions(e.g., discovery, SA, data and/or data patterns). The report may includethe average number of occupied and/or available resources (e.g.,discovery signal resources, SA, D2D data pattern) per subframe over adefined period (e.g., a discovery occasion, a D2D data schedulinginterval) and/or over a number of subframes. The report may include thetotal and/or average number of occupied and/or available resources persubframe (e.g., with an energy above and/or below a threshold, or basedon successfully detected SA, and/or based on successfully decodeddiscovery signals). The report may include whether a pattern is occupiedor available. A pattern may be considered occupied if one or moreresources (and/or transmission opportunities) within the pattern areconsidered occupied (e.g., based on energy level measurements on thoseresources). A WTRU may report an occupied pattern. A WTRU may report thenumber of occupied patterns over available patterns. A WTRU may providefor a configured pattern to report. For example, a WTRU may provide aconfigured pattern to report on whether the pattern is occupied or not.The report may include the minimum number of occupied and/or availableresources and/or subframe in which this minimum value occurred. Thereport may include the number of subframes within a defined period, forexample, in which x resources or less where available (e.g., or yresources or more where occupied), and/or where x and y are numbersconfigured by the network.

The report may include a metric that may indicate a percentage, a ratioor a number of resources that are occupied and/or available in asubframe and/or a set of subframes, for example, within a definedperiod. The report may include the metric during a period of time (e.g.,a D2D scheduling period). The report may include an average of thenumber of resources or the actual number of resources (e.g., or thepercentage of resources) on subframe(s) over a defined period (e.g., onesubframe, a plurality of subframes, and/or a discovery occasion) with ameasured energy level above a threshold, below a threshold and/or thoseresources for which a signal (e.g., SA<discovery, D2D data) wassuccessfully detected. The threshold may be configured by the network aspart of the configuration message and/or may correspond to the thresholdused by the WTRU to determine whether a resource is available fortransmission or not.

The report may include the amount of energy the WTRU measured. Theamount of energy may be measured on a resource(s) and/or on a set ofresources over a subframe and/or a set of subframes. The WTRU may reportan index to a resource, a plurality of resources (e.g., a pattern), themeasured energy level, and/or the subframe in which the measurement wastaken. The WTRU may report an index to a resource and/or an averagemeasured energy on the resource(s) over a period time. The report mayinclude the amount of energy on one or more resources with the largestenergy (e.g., largest X energy amounts).

The report may indicate that the network resource configuration may beinsufficient. The transmitting WTRU may be configured to report that theamount of resources currently allocated by the network (e.g., in thecurrent cell) are insufficient for the WTRU to meet the QoS and/ortransmission rate of the WTRU discovery process or D2D datatransmission. The WTRU may report after a new configuration is received(e.g., from the SIBs) and/or after the WTRU has changed cell (e.g., inIdle mode) and the amount of resources allocated in the new cell areinsufficient for the WTRU. The WTRU may report to the network the amountof resources required for the WTRU to meet its target QoS and/ordiscovery transmission rate, for example, as determined per the WTRUdiscovery processes configuration or D2D data transmissionconfiguration.

The report may include a report by a monitoring WTRU on the outcome ofdiscovery signal or D2D transmission decoding. For example, themonitoring WTRU may report a number and/or rate of failures and/orsuccesses on a dedicated resource, a plurality of resources, or areceived data pattern (e.g., for type 2 discovery, mode 1communications, or type 2 discovery) (e.g., the rate of successfulreception over one or more scheduled occasions. The report may indicatea decoding failure, which for example, may refer to when the monitoringWTRU fails to decode the discovery signal or D2D transmission on aresource. The report may indicate a decoding success, which for example,may refer to when the monitoring WTRU successfully decodes the discoverysignal on a resource. The report may indicate a decoding failure ordecoding success for one or more (e.g., a plurality of) resources. AWTRU may attempt decoding D2D transmissions on a particular resource setwithin a scheduling period (e.g., WTRU decoded the SA indicatingtransmission opportunities for the WTRU). A WTRU may count the number ofsuccessful or failed decoding attempts. A WTRU may count the number ofsuccessful or failed HARQ processes. A report may include decodingfailure for a plurality of resources (e.g., X out of Y HARQ processeshave failed or a percentage of the detected failures over totalreception opportunities within a scheduling period have been observed).The report may indicate the rate of a decoding failure and/or success,which for example, may refer to the ratio between the number of failuresand/or successes on a resource and/or a total number of decoding. Thenumber may be the total number of failures on each resource, the averagenumber of failures over all resources in a subframe, and/or the averagenumber of failures on a single resource over a number of subframes.

The report may indicate the number of resources on a subframe (e.g., oraverage thereof) in which the WTRU detected the presence of a discoverysignal or data transmission but failed to successfully decode thesignal. The WTRU may consider that it detected the presence of adiscovery signal when one or more of the following occurs: the receivedtotal energy measured over the resource is above a threshold and/or thereceived level of a reference signal measured over the resource (e.g., acorrelator implementation) is above a threshold. The reference signalmay be a signal of known properties.

The WTRU may determine a failure to decode based on a cyclic redundancycheck (CRC) transmitted, for example, along with the remaining payloadof the discovery signal. The CRC may be masked with a RNTI known by thereceiving WTRU, for example, within a period The period may beconfigurable. The period may be the last Z resource allocation period(e.g., a frame, a period represented by Y TTIs, Y ms, and/or Y frames,and/or the like). The WTRU may determine a success to decode a signalbased on successfully receiving and/or verifying a CRC.

The report may indicate the number of resources in which a discoverysignal was received on a subframe and/or a number of subframes. Thereport may indicate the number of failed decoding attempts and/or numberof subframes in which a discovery signal was successfully decoded and/orpassed to higher layers.

The report may indicate an index of the resource(s) on which themonitoring WTRU fails to decode the discovery signal(s), for example,within a period. The period may be configurable. The period may be thelast Z resource allocation period (e.g., a frame, a period representedby Y TTIs, Y ms, and/or Y frames, and/or the like). The report may besent by a monitoring WTRU. The report may include a number ofsuccessfully decoded SA transmissions in a time interval. The report mayinclude the number of successfully decoded SA transmissions for theassociated data transmission, for example, as determined by theidentifier in the SA or via the higher layers (e.g., MAC header, ProSEIdentifier, etc.). The report may include the identity associated withan SA that may be determined to cause issues, such asinterference/near-far effect. The report may include the identityassociated to an SA for which SA detection may be successful but datareception may fail (e.g., for a duration of time).

The report may include an interference level that measured by the WTRU.The WTRU may be configured perform a noise measurement, for example at anoise measurement occasion. For example, the network may not schedule aD2D or cellular communication during one or more subframes and the WTRUmay perform the noise measurement during the unscheduled subframe(s).The WTRU may take noise measurement periodically, for example at one ormore interference measurements occasions. The WTRU may be configured tomeasure the level of interference over the set of allocated D2Dresources (e.g., discovery time/frequency resources). The WTRU may beconfigured to report the level of interference above the noise levelbased on a measurement. The WTRU may be configured to report when themeasurement is above or below a configured threshold.

The report may be bound in size, for example, such that at most a numberof elements are included in the report and/or a maximum number ofreference period(s) may be reported.

There may be one or more triggers for the WTRU to create (e.g.,generate) and/or send (e.g., transmit) the report. For example, the WTRUmay initiate the creation and/or transmission of a report when itreceives L3 signaling that requests a report. The WTRU may initiate thetransmission of a report when the WTRU is configured for reporting andanother trigger initiates transmission of the report. The signaling maybe specific to a discovery process and/or event (e.g., associated to asingle identity), to a subset of discovery processes and/or events(e.g., associated with one or more identities and/or per type ofresource allocation), and/or may be WTRU-specific (e.g., applicable toone or more identities). For example, the WTRU may initiate thetransmission of a report if there is at least one or more transmissionsapplicable for the reporting period. The WTRU may transmit the reportsalone and/or as part of a message reporting successful decoding of adiscovery signal of interest, for example, to the ProSE server. TheProSE server may forward the report to the RAN and/or provideinformation (e.g., load/configuration information) to the RAN, the MME,eNB, etc.

The WTRU may initiate the creation and/or transmission of a reportperiodically, for example, if there is at least one or moretransmissions applicable for the reporting period. For example, thereporting may be periodic at the end of a discovery occasion and/orafter a number of discovery occasions. A WTRU may be configured toreport periodically in D2D communications, for example, along aperiodical BSR.

The WTRU may initiate the creation and/or transmission of a report in anaperiodic manner. The WTRU may initiate the transmission of a report viathe reception of control signaling that requests that the WTRU performthe reporting. The signaling may be received from a network node. Thesignaling may be dedicated signaling and/or signaling applicable to aplurality of WTRUs (e.g., received on a broadcasting channel and/or on acommon control channel). For example, signaling may be carried alongwith a grant transmitted by an eNB. The WTRU may initiate thetransmission of a report in an aperiodic manner, for example, if thereis at least one or more transmissions (e.g., configurable transmissions)applicable for the reporting period.

The signaling may indicate one or more WTRUs (e.g., using a commonidentity, such as scrambling of a request using a common RNTI and/or arequest sent on a common control channel). The signaling may indicateone or more WTRUs configured with at least one resource allocation(e.g., a WTRU configured for discovery and/or for direct WTRU-to-WTRUcommunications). The signaling may indicate the resource allocation forwhich the reporting is applicable. For example, the control signalingmay include resource allocation information and/or indexing, forexample, such that a WTRU may determine whether or not it corresponds toone or more of its resource configurations. If the WTRU determines thatthe resource allocation information and/or indexing correspond to one ormore of its resource configurations, the WTRU may initiate the reportingfor the resource. The signaling may indicate the identity of the processand/or event. For example, the control signaling may include anidentity, for example, such that a WTRU may determine whether or not itcorresponds to one or more of its processes. If the WTRU determines thatthe identity of the process and/or event corresponds to one or more ofits processes, the WTRU may initiate the reporting for the resourcesassociated to the process and/or event. The WTRU may initiate thecreation and/or transmission of a report based on a change of operationstatus. For example, the report may be triggered after the last subframeof the discovery period and/or occasion. The WTRU may report to thenetwork when it resumes normal operation with the eNB. The report may betriggered after a scheduling period is completed. For example, a WTRUmay transmit a report after a configurable number of scheduling periods.

The WTRU may initiate the creation and/or transmission of a report basedon an outcome of a discovery or data transmission process and/or event.For example, the WTRU may initiate reporting when it determines that thediscovery or transmission of data is not successful. For example, theWTRU may initiate reporting when the WTRU has determined that thediscovery or data transmission has not been successful for a certainperiod of time and/or for a certain number of attempts (e.g., a periodwith at least one transmission of a discovery signal), which may beconfigurable aspects of the reporting.

The WTRU may initiate the creation and/or transmission of a report basedon an outcome of SA reception/transmission. A WTRU may initiatereporting when it determines that reception of a configurable number ofSA is not successful. A WTRU may initiate reporting when it determinesthat it may not have transmitted the SA a configurable number of times,for example, when no SA resource is available.

The WTRU may initiate the creation and/or transmission of a report basedon an outcome of the physical layer discovery signal decoding by amonitoring WTRU. For example, the WTRU may initiate a report to thenetwork when it determines that a certain rate of decoding failuresand/or successes has been reached. For example, the report may betriggered when the WTRU detects that a certain number of decodingfailures have occurred in one or more allowed discovery subframes or D2Dcommunications subframe (e.g., as defined by transmission pattern).

The report may be triggered when the WTRU detects a failure trigger by amonitoring WTRU. A report may be triggered when the WTRU fails to decodea configured number of discovery signals or data reception opportunitieson one or more resources, for example on a subframe and/or over a numberof subframes (e.g., consecutive subframes, a number of subframes over aconfigured period, as indicated by a data pattern, and/or the like). Areport may be triggered when the rate of decoding failures of D2Dtransmission (e.g., a discovery signal or D2D data) is above a thresholdon a subframe and/or a number of subframes (e.g., consecutive subframes,a number of subframes over a configured period, and/or the like). Therate of decoding failure may be determined to be the number of faileddecoding attempts over the number of total decoding attempts onresources in which a discovery signal is being transmitted. The rate ofdecoding failure may be determined to be the number of failed decodingattempts over the total number of monitoring resources. A report may betriggered when a WTRU determines the rate of failure of SA or D2D datacommunications (e.g., in terms of block error rate, BER, outage, etc.)during a period of time. A report may be triggered when a WTRU reportsto the network when the rate of failure is larger than a threshold.

A report may be triggered based on the success of packets decoded (e.g.,the number of successfully decoded packets over the total number ofattempts).

A report may be triggered based on an outcome of a transmission attemptby a transmitting WTRU. For example, the WTRU may initiate thetransmission of a report based on the outcome of a transmission attempt(e.g., failure to transmit, the number of attempts before a successfultransmission, and/or the like). A failure to transmit may refer to theWTRU not finding an available resource for transmission on a discoveryresource (e.g., an allowed discovery resource) in one or more discoverysubframes (e.g., allowed discovery subframes). An attempt to transmitmay include the WTRU trying to transmit a discovery signal over one ormore allowed resources, for example, on a discovery subframe. Asuccessful transmission may include the WTRU finding an availableresource for transmission and/or transmitting the discovery signal overthe air. For example, attempt to transmit may refer to a WTRU trying totransmit an SA and/or the associated D2D data, such as for D2D datacommunications. A successful transmission may refer to a WTRU findingavailable resources for transmission of the SA and the associated D2Ddata, such as in D2D data communications.

The WTRU may initiate the creation and/or transmission of a report basedon a failure to transmit. For example, the WTRU may initiate thecreation and/or transmission of a report as a result of failures totransmit at least a discovery signal in a set of available discoveryresources (e.g., resource pool). The failure to transmit may be when theWTRU fails to transmit in a given sub-frame or a set of sub-frames. Thefailure to transmit may be when the WTRU fails to transmit the discoverysignal within a discovery occasion. The failure to transmit may be whenthe WTRU fails to find a resource for transmission over a configuredperiod of time. The failure to transmit may be when a WTRU fails totransmit an SA and/or associated data within a period (e.g., the periodfor which a network grant may be valid). The failure to transmit may bewhen a WTRU fails to find a resource for transmission of an SA and/orassociated data within a period (e.g., the period for which a networkgrant is valid). The failure to transmit may be when the WTRU detectsthat it failed to transmit a configured number of times during a periodof time T. For example, the failure count over a period of time may berelated to multiple transmissions of discovery signals within adiscovery occasion and/or multiple discovery occasions, or for D2D datacommunications to one or more PDCP, MAC or RLC PDUs (e.g., the WTRU mayhave X failures among Y discovery subframes within a discovery period, aWTRU may have X MAC PDU failures among Y new data transmission occasionswithin a scheduling period). The failure to transmit may be when theWTRU detects that the number of failures for a discovery signaltransmission attempt is above a threshold within a configured period oftime (e.g., if for each attempt to transmit a discovery signal the WTRUfails to transmit for a period of time). The failure to transmit may bewhen the WTRU fails to transmit over a configured number of consecutiveallowed discovery subframes. The failure to transmit may be when theWTRU fails to find sufficient resources for transmission to achieve thetarget QoS and/or discovery transmission rate over a configured periodof time.

The WTRU may initiate the creation and/or transmission of a report basedon a number of attempts before a successful transmission. For example,the WTRU may report to the network based on the number of attemptsbefore the WTRU successfully transmits one or more a discovery signalsor D2D data communications signals. The report may be triggered when theWTRU has more than X tries before a success for a given transmissionand/or a number of transmissions. The report may be triggered when theaverage time before success for a given WTRU is larger than a threshold.The report may be triggered when the success rate (e.g., the number ofsuccesses/the total number of tries) is lower than a threshold.

The WTRU may initiate the creation and/or transmission of a report basedon a measured resource utilization. For example, the WTRU may initiate areport based on a measured resource utilization status. The report andresource utilization may be measured by a transmitting WTRU and/or amonitoring WTRU. A discovery measured resource utilization may refer toa WTRU performing a measurement on a discovery resource in one or moresubframes and/or measuring the energy level on the resource.

A trigger related to resource utilization may be when the number ofresources (NR) with measured energy below a threshold in a subframe isbelow a configured threshold, for example, over a period of time. Theperiod of time may be, for example, a subframe, a configured number ofsubframes, a number of consecutive subframes, a percentage of alloweddiscovery subframes within a discovery occasion, and/or the like. Atrigger related to resource utilization may be when the number ofresources (NR) with measured energy above a threshold in a subframe isabove a configured threshold over a period of time.

A trigger related to resource utilization may be when the averagemeasured energy over all or a subset of discovery resources in subframeis above or below a threshold, for example, for a period of time. Atrigger related to resource utilization may be when the ratio ofresources with measured energy below or above a threshold over the totalnumber of discovery resources in a subframe is below or above athreshold, for example, over a period of time.

A trigger related to resource utilization may be when the WTRUdetermines that the resource utilization over a configured period oftime (e.g., based on the ratio and/or number of resources with measuredenergy below or above a threshold) is insufficient for the WTRU to meetthe target QoS and/or discovery transmission rate.

The WTRU may initiate the creation and/or transmission of a report basedon a measured resource utilization in, for example, D2D communications.For example, a WTRU may initiate a report based on a measured resourceutilization status, for example, in D2D communications. The report andresource utilization may be measured by a transmitting WTRU and/or amonitoring WTRU.

A trigger related to resource utilization may be when the number of SAresources successfully decoded is above a configured threshold.

A trigger related to resource utilization may be when the number of SAresources successfully decoded is below a configured threshold.

A trigger related to resource utilization may be when the number of D2Ddata PRB (e.g., as indicated by the aggregated received SAs) is above aconfigured threshold.

A trigger related to resource utilization may be when the number of D2Ddata PRB (e.g., as indicated by the aggregated received SAs) is below aconfigured threshold.

A trigger related to resource utilization may be when the energymeasured in a configured plurality of PRBs (e.g., associated to D2D datacommunications) is above a threshold.

A trigger related to resource utilization may be when the energymeasured in a configured plurality of PRBs (e.g., associated to D2D datacommunications) is below a threshold.

A trigger related to resource utilization may be when a WTRU determinesthat the resource available may be insufficient to meet the targetand/or required QoS for a D2D data transmission service (e.g., VoIP,video streaming, etc).

A WTRU may be configured to trigger transmission of a report upondetection of a change in coverage situation and/or D2D transmission mode(e.g., Mode 1 (eNB controlled), Mode 2 (non-eNB controlled)). A WTRU maybe configured to trigger transmission of a report. A WTRU may beconfigured to trigger transmission of a report when a WTRU enters eNBcoverage. For example, a WTRU may detect that it has uplink coveragewhen a WTRU successfully connects to the eNB (e.g., RRC connectedstate).

A WTRU may be configured to trigger transmission of a report when a WTRUenters Mode 1. A WTRU may be configured to transmit a report when a WTRUis configured to operate in Mode 1.

A WTRU may be configured to trigger transmission of a report when a WTRUchanges cells. A WTRU may be configured to transmit a report to a neweNB, for example, after a handover. A WTRU may be configured to transmitupon transmission of a tracking area update. A WTRU may be configured totransmit when a WTRU is configured with D2D data communications andchanges cell, for example, in Idle mode.

The WTRU may transmit a report using L2 (e.g., MAC) signaling (e.g., asa MAC Control Element), as L3 (e.g., RRC) signaling (e.g., as a RRC PDU,for example, as part of a reporting procedure), and/or as higher layersignaling (e.g., NAS signaling, application signaling, and/or the like).For example, the WTRU may receive control signaling on the PDCCH (e.g.,an aperiodic request) that triggers reporting. The WTRU may assemble thereport as a MAC control element and include it in an uplink transmission(e.g., the next uplink transmission). The eNB may be the endpoint of thereporting procedure.

The WTRU may receive a request on a signaling radio bearer (SRB) as anRRC PDU that triggers reporting. For example, the WTRU may assemble thereport as a RRC PDU and make it available for transmission on the SRB.

The WTRU may trigger reporting at the application level. For example,the WTRU may assemble an application layer control packet and make itavailable for transmission as a RRC PDU (e.g., and make it available fortransmission on the concerned SRB (e.g. in case NAS is used)) and/or asa user plane data (e.g., and make it available for transmission for acorresponding DRB). The ProSe and/or the application server may be theendpoint of the reporting procedure.

The WTRU may trigger reporting if the WTRU is in RRC IDLE mode. Forexample, the WTRU may initiate a transition to CONNECTED mode andtransmit the report according to the applicable signaling method. TheWTRU may remain in IDLE mode and delay the transmission of the reportuntil it moves to CONNECTED mode, for example, if RRC and/or a higherlayer protocol is used.

A network node (e.g., a base station, for example an evolved Node B(eNB)) may receive the report. The network node that receives the reportmay determine the blocking rate for a given resource, for example, ifthe report is received from multiple sources. The network node thatreceives the report may initiate a procedure that reconfigures theresources for one or more WTRUs such that the estimated rate may belower, for example, if the rate is above a certain threshold.

Discovery signal transmission control for resource management may beprovided. A network entity (e.g., an eNB, a ProSe server, and/or thelike) may have direct control over the transmission of discoverysignals, for example, for the purpose of managing resources allocated toD2D.

A WTRU may suspend and/or resume transmission of a discovery signal inone or more resources following the reception of signaling from thenetwork. The network may utilize this functionality, for example, toassess the level of interference and/or the load generated by one ormore WTRUs and/or to diagnose and/or temporarily relieve a congestionsituation in a resource. For example, the network may determine that aWTRU may cause excessive collisions and/or interference to other WTRUsin a resource by suspending transmissions from the WTRU and/or receivingreports from one or more other WTRUs that indicate improved performanceafter the suspension. The network may take corrective actions, forexample, re-assigning the WTRU to a different set of resources,restricting the WTRU to use a resource within a specific set ofresources (e.g., a resource from a particular resource pool), increasingthe amount of resources available for discovery signal transmissions,and/or the like. When the WTRU receives signaling indicating suspensionof transmission, the suspension may remain effective for a certainduration (e.g., until expiration of a timer started upon reception ofthe signaling) and/or until reception of signaling indication resumptionof transmission. The duration of the timer may be configured by higherlayers and/or may be indicated in the signaling.

The suspension and/or resumption of transmission may apply to one ormore discovery signals that are transmitted by the WTRU. The suspensionmay be applicable to one or more (e.g., a subset of) resources. Thediscovery signal(s) and/or resources may be indicated in the signaling.

A WTRU may initiate transmission of one or more discovery signals in oneor more resources following the reception of signaling from the network.The transmission may take place even if the WTRU would not haveotherwise triggered transmission of a discovery signal, for example,based on an application and/or based on a configuration from a ProSeserver. The network may utilize this functionality, for example, tocontrol the load from discovery signal transmissions over a period oftime where other WTRU's are configured to measure and/or report over aresource, for example, according to examples provided herein. This mayallow the network to obtain information on a potential collision and/orinterference issue between WTRUs more reliably and/or quickly thanotherwise.

When the WTRU receives a transmission order (e.g., as per the above), aproperty of the discovery signal may be set to a specific value. Theproperty may include the resource used for the transmission of thediscovery signal, the discovery payload, an RNTI used to mask a CRC usedfor decoding the discovery signal, a value and/or configuration of thedemodulation RS, and/or the like

A value of a property may be configured by higher layers, bepre-determined, and/or be indicated in the signaling. A receiving WTRUmay determine that a received discovery signal that has a property setto a specific value was transmitted for control and/or managementpurposes (e.g., only for control and/or management purposes). Thereceiving WTRU may determine that the received discovery signal may notinclude useful information to be passed to higher layers (e.g., exceptfor reporting performance).

A WTRU that measures and/or reports over a resource may monitor one ormore discovery signals that match the at least one property. The WTRUmay transmit (e.g., periodically transmit) a discovery signal accordingto the above properties without receiving a signaling order. Thetransmission instances and/or property values may be configured byhigher layers.

Signaling mechanisms in support of discovery transmission control may beprovided. The signaling may be received at the physical layer, at theMAC and/or RRC sublayers, and/or at higher layers. For example, a WTRUmay monitor downlink control information in a search space (e.g., thecommon search space) using an RNTI. The RNTI may be common to one ormore WTRUs configured to transmit discovery signals.

The signaling may include a paging message, for example, received at theWTRU's paging occasion and/or at a paging occasion used for the purposeof discovery transmission control.

The signaling may include an indication (e.g., explicit indication) ofthe identity and/or set of identities of the WTRU and/or discoverysignal(s) related to the command. A set of identities may be indicatedwith a group identifier. The mapping between a group identifier and aset of identities may be configured by higher layers (e.g., a WTRUtransmitting a discovery signal may be configured with a groupidentities, for example, for the purpose of transmission control) and/ormay include of a subset of bits (e.g., least or most significant bits)of the WTRU and/or discovery signal identity.

A WTRU may determine to act on the received signaling probabilistically.For example, the WTRU may draw a random number (e.g., between 0 and 1)and determine that it is concerned by the received signaling if therandomly picked number is below (e.g., or is above) a threshold. Thethreshold may be pre-determined, indicated in the signaling, and/orpre-configured by higher layers. The use of a threshold may allow thenetwork to control the percentage of WTRUs and/or the percentage ofdiscovery signals concerned by an order to initiate and/or suspendtransmission.

A single signaling order may be interpreted as a suspension order by oneor more WTRUs and/or as a transmission order by other WTRUs. Forexample, a WTRU receiving signaling may determine that it may initiatetransmission of a discovery signal if its identity is included in afirst signaled group identity. The WTRU receiving signaling maydetermine that it may suspend transmission of discovery signal(s) if itis not included in the first group identity and/or if it is included ina second group identity included in the signaling.

The signaling for controlling transmission for a first subset of WTRUsand/or discovery signal identities may be combined with signaling usedfor triggering the measurement and/or reporting over a discoveryresource for a second subset of WTRUs and/or discovery signalidentities.

Mechanisms to allow WTRUs to coordinate resource usage may be provided.Once a WTRU is configured with resources for transmission of a discoverysignal, the WTRU may perform transmissions accordingly. If the WTRU isin-coverage with an eNB, the resource pool and/or dedicated resourcesmay be preconfigured and/or dynamically configured by the network. Ifthe WTRU is out-of-coverage of an eNB, the WTRU may obtain resourceconfiguration from a stored pre-configuration and/or from a coordinatingentity (e.g., cluster-head). The resources used by the transmitting andreceiving entities may be coordinated, for example, ifdiscovery/communication is supported when WTRUs in the coverage of thesame configuring entity and/or associated with configuration entitiesthat coordinate with each other. Issues may arise when a WTRU performstransmission and/or reception in multiple domains at the same time, forexample, if the discovery/communication is supported in scenarios whichare not coordinated.

For resource allocation, the WTRUs may be pre-configured with a resourcepool to transmit/receive when operating in out-of-coverage mode. Inparticular, all WTRUs may be also preconfigured with resources totransmit and receive the resource configuration information (e.g. whereto send control information message e.g. synchronization message). TheWTRU may also be configured by a controlling entity what resources touse within a resource pool.

FIG. 6 is a diagram illustrating an example of scenarios forin-coverage, out-of-coverage, and partial coverage D2D discovery and/orcommunications.

The in-coverage WTRU may discover and/or be discovered by neighboringWTRUs that may be controlled by other uncoordinated controlling entitiesand/or may be operating in a different spectrum. Since the eNB mayprovide resource pools for in-coverage discovery, the WTRU may not beable to discover and/or be discovered by the neighboring WTRU, forexample, if the neighboring WTRU is not monitoring the same resourcepool. The in-coverage WTRU may move (e.g., autonomously move) to apublic safety (PS) spectrum and/or out-of-coverage spectrum to performreception and/or transmission, however, for example, without networkcoordination this may result in loss of data and/or loss of pagingreception. Mechanisms to allow coordination between the eNB and thein-coverage WTRUs may be provided.

An in-coverage WTRU may determine to perform communication with an outof coverage WTRU, act as WTRU-to-Network relay with another WTRU, and/ordetermine to perform communication with a neighboring WTRU that maydetermine the set of resources to use by a pre-configuration and/or by acontrolling entity (e.g., a cluster head) which may not be coordinatedwith the serving eNB. The resources and/or time used for transmission bya neighboring WTRU may correspond to subframes in which the in-coverageWTRU may be performing normal cellular communications. The in-coverageWTRU may coordinate with the eNB to request time and/or resources inwhich it can communicate with the neighboring WTRU without negativelyimpacting the cellular connection with the eNB.

The WTRU may switch (e.g., autonomously switch) to transmitting and/orreceiving on the resources in which the neighboring WTRU is expecting toreceive and/or transmit. This may result in data loss, the WTRU nottransmitting in the UL, and/or missing paging occasions while in idlemode. In order to avoid data losses and/or loss of paging, coordinationbetween the eNB, the in-coverage WTRU, the out-of coverage WTRU, and/orthe controlling entity out-of coverage WTRU may be provided, forexample, for the WTRUs using a single transmit and/or receive. Thecoordination may involve coordination of time patterns in which thiscommunication is expected to happen and/or a coordination of resources(e.g., frequency and/or time) in which this communication and/ordiscovery may take place.

The coordination may aim at allowing controlling entities to align theresources that the WTRUs involved in the communication are using and/orto be aware of scheduling restrictions during these time periods.

The network and/or coordinating entity may be made aware of resourceallocation conflicts, for example, such that the network may re-allocateresources and/or schedule the WTRUs accordingly. For example, this maybe performed for communication across different clusters that may becontrolled by different entities. The eNB may refer to a cluster headand/or controlling entity in a group and/or cluster. The in-coverageWTRU may refer to a WTRU that is connected to the cluster head and/orcontrolling entity. A neighboring WTRU, PS WTRU, and/or out-of-coverageWTRU may refer to a WTRU that is configured to operate in directcommunication. The resource pool and/or configuration for theneighboring WTRU, PS WTRU, and/or out-of-coverage WTRU may be controlledby an uncoordinated controlling entity different from the in-coverageWTRU and/or for which the resources are pre-configured.

The methods described herein relating to in-coverage and out-of-coveragemay be applicable to allow coordination between a WTRU that may becontrolled by different uncoordinated controlling entities or eNBs, etc.

An in-coverage WTRU may coordinate, request a gap(s), and/or requestresources to communicate with an out-of-coverage WTRU. FIG. 7 is adiagram of an example scenario of communication between an in-coverageWTRU and an out-of-coverage WTRU. Interactions between an in-coverageWTRU and an out-of-coverage WTRU, for example, to negotiate resourceallocation for the out-of-network link (e.g., PC5) may be provided.Interaction between the in-coverage WTRU and an eNB, for example, tosupport resource reconfiguration and/or gap/pattern configuration may beprovided. The examples described herein may apply to the case where anin-coverage WTRU performs direct public safety communication on publicsafety resources.

Methods to negotiate resource allocation for out-of-coverage link may beprovided. The in-coverage WTRU may have a coordinated time and/or gappattern, for example, such that it may tune out of the cellular linkwithout the risk of losing data. The out-of-coverage WTRU may be awareof when and/or where to expect to receive and/or transmit, for example,to ensure that interested parties may receive the communication.

A pattern for communication may refer to a time pattern (e.g., a period,a cycle, a duration, and/or the like) in which the WTRU may transmitand/or receive. A pattern for communication may refer to a time patternfor reception and a time pattern for transmission. A pattern forcommunication may include resource information, for example, such afrequency, subframe(s), PRB(s), and/or the like.

An out-of-coverage WTRU may determine and/or drive resource allocation.FIG. 8 is a diagram of an example of signaling that may be used for anout-of-coverage WTRU to determine and/or drive resource allocation.Resource allocation may refer to a time, a gap pattern, and/or a timeand/or frequency configuration for the PS link. For example, theout-of-coverage WTRU may provide and/or broadcast (e.g., in a knownpre-configured resource) the resource allocation configuration it isconfigured to use and/or is using for communication. Resource allocationmay be in the form of an SA, a broadcast synchronization message, acontrol message, and/or the like. The resource configuration may includethe time and/or frequency pattern in which the PS WTRU is expecting totransmit and/or receive.

The WTRU may provide a resource configuration if it determines that anin-coverage WTRU is present. The WTRU may provide the resourceconfiguration periodically or all of the time and/or prior to datatransmission. The WTRU may provide the resource configuration when WTRUsoperating in different spectrums are expected.

A WTRU (e.g., an in-coverage WTRU) may receive (e.g., from anout-of-coverage WTRU) a configuration and/or a time pattern. The WTRUmay communicate the configuration information in a report to the eNB.The information communicated to the eNB may include a recommended gappattern and/or frequency resources for the out-of-coverage WTRU, forexample, for the out-of-coverage WTRU to use to communicate. Thein-coverage WTRU may determine to send this information to the eNB, forexample, if it determines that the out-of-coverage WTRU is a WTRUbelonging to the same group as in the in-coverage WTRU (e.g., the WTRUis allowed to receive from this device). The eNB may reconfigure theresource pool it uses (e.g., for discovery and/or communication) and/orprovide the in-coverage WTRU with gaps and/or scheduling opportunitiesto listen to the out-of-coverage link, for example, according to theresources provided by the out-of-coverage WTRU. The eNB may provide thegap pattern. The eNB may approve the use of the suggested gap pattern.

The gap pattern may be translated and/or adjusted according to thetiming used by the controlling entity, for example, in the case wherethe timing and/or reference frame numbers used to determine thescheduling opportunities are different between an in-coverage WTRU and aneighboring WTRU.

Resource allocation may be determined and/or driven by the eNB and/orthe in-coverage WTRU. FIG. 9 is a diagram of an example of signalingthat may be used for an eNB and/or an in-coverage WTRU to determineand/or drive resource allocation. The resource usage allocation for anout-of-coverage link may be driven by the in-coverage WTRU and/or theeNB. For example, the out-of-coverage WTRU may transmit (e.g.,broadcast) a resource allocation pool that it may use to selectresources for operation and/or the in-coverage WTRU may be aware of theresource pool according to the pre-configured information. Thein-coverage WTRU, for example once it detects an out-of-coverage WTRU,may determine the resource pool the neighboring WTRU is using. Thein-coverage WTRU may not receive this information from theout-of-coverage WTRU and/or it may rely on the preconfigured resourcepool for the PS it has. The network may be aware of the resource poolpre-configured for the PS WTRUs.

The WTRU (e.g., in-coverage WTRU) may send a report to the eNB, forexample, based on one or a combination of the triggers described herein(e.g., upon detection of the need to communicate to as a PS WTRU and/orcommunicate to a neighboring WTRU). The content of the report may bedescribed herein, for example, the report may include the resource poolthat the PS WTRU may be using, recommended time pattern, pre-configuredtime pattern, etc.

The eNB, for example upon reception of this request, may determine thescheduling opportunities and/or gaps to allocate to the in-coverage WTRUfor PS communication and/or discovery and/or may send the gap patternand/or time pattern and/or resource configuration to the WTRU orapproves the use of the requested time pattern.

In the case of idle mode operation, the in-coverage WTRU, for example,based on the discovery resource pool allocated for in-coverage (e.g.,time pattern and/or frequency) and/or the paging occasions, maydetermine a time pattern that may allow the in-coverage WTRU to tune outof the serving eNB and successfully perform communication with theneighboring WTRU.

The in-coverage WTRU may be configured by the eNB with a reception timepattern for communication with other WTRUs (e.g., in-coverage and/orout-of-coverage to the eNB) and/or the in coverage WTRU may have thepattern pre-configured.

The in-coverage WTRU, for example based on the determined pattern (e.g.,from the eNB and/or determined internally), may send a message and/orreport to the neighboring WTRU. The message may be transmitted as abroadcast message, as a synchronization message, and/or as a dedicatedmessage to the WTRU and/or by using a control message that may bereceived by WTRUs belonging to the same group. The message and/or reportmay indicate the resource allocation, time pattern, and/or frequency inwhich the in-coverage WTRU may transmit and/or receive. The neighboringWTRU may relay and/or transmit (e.g., broadcast) the message and/orpattern to its controlling entity, which for example, may approve and/orconfigure the neighboring WTRU with the requested pattern and/or maysend a new suggested pattern.

The eNB, for example in addition to a gap pattern and/or time pattern,may provide the WTRU with a specific resource configuration (e.g.,frequency and/or time, for example by specifying subframe(s) and/orPRB(s)) that the out-of-coverage WTRU may transmit and/or receive within-coverage WTRU, where for example, the frequency may correspond to thein-coverage resource pool. The out-of-coverage WTRU may be a standaloneunattached out-of-coverage WTRU that may be trying to connect to thenetwork using the in-coverage WTRU as a WTRU-to-NW (network) relay. Theout-of-coverage WTRU may be communicating with other in-coverage and/orout-of-coverage WTRUs.

Interactions between an in-coverage WTRU and an out-of-coverage WTRU maybe provided. When the WTRU begins to operate in the relay and/or PSmode, the WTRU may send one or more D2D synchronization signals (D2DSS)and/or a control message (e.g., synchronization message). The WTRU mayadvertise that it is capable of operating as a relay and/or PS node inthe control message. A neighboring WTRU operating in vicinity which islooking for a coordinating entity may monitor (e.g., periodicallymonitor) for D2DSS control symbols and/or may detect the WTRU (e.g., incoverage WTRU, out of coverage WTRU, relay WTRU, and/or the like). Thetriggers for a WTRU to begin operating as a relay node may be based onpre-configuration, based on measurements, based on explicit trigger fromthe network and/or from the ProSe server, and/or the like.

The in-coverage WTRU may send resource pool information, obtainsacknowledgements, send a report to the eNB, and/or the like. The WTRUoperating as a relay and/or triggered to operate as a PS node mayoperate in an unsolicited mode. For example, the WTRU may advertiseitself as a relay and/or a PS node. The WTRU may send an advertisementmessage with one or more ProSe parameters (e.g., ProSe WTRU id,security, ProSe group id, etc.) and/or the resource pool it may be usingfor a link with the out-of-coverage WTRU and/or other PS nodes. The WTRUmay operate as a cluster-head and/or append this information as a partof cluster configuration message, for example, for the synchronizationmessage. This may be used by the WTRU to support open discovery. Thecontrol message may carry resource configuration provided by the eNB.

The out-of-coverage WTRU may send a response accepting the configurationparameters. The response message may indicate one or more (e.g., asubset) of the resources in the pool that are acceptable to theout-of-coverage WTRU. The relay and/or the PS node WTRU may send areport to the eNB with this information, for example, as describedherein. The eNB may accept this configuration. The eNB may configuregaps and/or reconfigure resources for the relay WTRU and/or PS node tobe able to operate with the out-of-coverage WTRU and/or PS node usinggaps.

Resources may be used for relaying a control message (e.g.,synchronization message). A WTRU operating as a relay may request forresources to relay the control message. The WTRU operating as a relaymay use semi-statically allocated resources signaled by the eNB (e.g.,using SIB signaling) to relay the control message. The WTRU operating asa relay may use preconfigured resources to relay the control message.The resources may be explicitly preconfigured for a control messageand/or the WTRU may select (e.g., autonomously select) resources from aresource pool to be used for relaying the control message.

The out-of-coverage WTRU may request resource pool information, obtaininformation, send a report to the eNB, and/or the like. The remoteand/or PS node WTRU may send a solicitation message requesting anyneighboring WTRUs that can operate in a relay and/or PS mode. The WTRUmay operate as a cluster-head. The WTRU may include the resource pool itexpects to use for transmission and/or reception and/or is using in thecluster configuration message, for example, for the synchronizationmessage. A WTRU (e.g., with capability to operate in relay and/or PSmode, and/or operating in solicited mode) may detect this node and/orrespond by declaring itself as a relay and/or PS node. The responsemessage may indicate the parameters identifying itself as a ProSe node(e.g., ProSe WTRU id, ProSe group id, etc.), security configuration,and/or the like. The responding WTRU may request a different resourcepool, for example, based on capabilities and/or an existing gap patternconfiguration.

The relay and/or the PS node WTRU may send a report to the eNB with thisinformation (e.g., as described herein), for example, once the resourcenegotiation is concluded. This mode may support targeted discovery. TheeNB may accept the configuration and/or configure gaps and/orreconfigure resources for the relay WTRU and/or PS node to be able tooperate with the out-of-coverage WTRU and/or PS node using gaps.

Methods to coordinate a communication from a coordinating WTRU may beprovided. The WTRU may send a report. The WTRU may identify one or more(e.g., all) of the resources in the report. A reporting mechanism, aWTRU, and/or a WTRU transmitting a message may be used to allowcoordination of time and/or resources used by WTRUs in coverage ofdifferent cells and/or clusters controlled by uncoordinated entities.Reporting may include resource allocation for an out-of-coverage link toassist the controlling entity and/or transmitting entity to determinescheduling opportunities and/or resource allocation. Resource allocationinformation may include information relayed, transmitted, broadcasted byneighboring WTRUs, and/or available (e.g., configured or preconfigured)in the in-coverage WTRU.

Reporting (e.g., which may include format, triggers, time windows,and/or the like) may be configured by the network (e.g., by a networknode such as an eNB). The network node may configure one or more WTRUsthat are configured to operate in a certain D2D communication mode. Thereception of this report by the network may trigger actions.

The report may be transmitted to a coordinating entity and/or may betransmitted in the form of a broadcast message, as a part of asynchronization message, as a dedicated message by the coordinating(e.g., in-coverage) WTRU, and/or the like.

The report and/or the transmitted message triggered by a WTRU mayinclude resource configuration from neighboring WTRUs. For example, thereport may indicate the resource pool information obtained from theneighboring entities (e.g., WTRUs, cluster heads and/or eNBs, and/orout-of-coverage WTRUs).

The reported configuration may include the resource set intended for D2Ddiscovery (e.g., frequencies, bandwidth, subframe(s), PRB(s), time,and/or the like), the resource set intended for D2D communications(e.g., frequency, bandwidth, subframe(s), PRB(s), time, and/or thelike), and/or the identity of the coordinating entity and/or of the WTRUproviding configuration information (e.g., cluster head id, eNB idand/or WTRU id, group ID, Prose ID, and/or the like).

The report triggered by a WTRU may include resources (e.g., a sub-set ofresources) within a resource pool or the resource pattern that thein-coverage WTRU requests from the eNB (e.g., or may use as previouslyreceived from the eNB and/or already configured in the WTRU), forexample, such that it may communicate with the out-of-coverage WTRU. Forexample, the report may include a suggested and/or used time pattern(e.g., cycle, duration, etc.), frequency, and/or the like. The reportmay indicate a controlling entity that may be taken into account and/orgrant to the reporting WTRU. The suggested time pattern may be receivedfrom the neighboring WTRU and/or determined (e.g., autonomously) by thein-coverage WTRU based on information it has available. For example, thereport may include one or more indices describing the resource(s) (e.g.,in time and/or frequency) within a resource pool which theout-of-coverage WTRU and in-coverage WTRU have negotiated and/orpreconfigured to use for the out-of-network link.

The report triggered by a WTRU may include location information.Location information may be associated with the reporting WTRU and/ormay be associated to the report. A WTRU (e.g., transmitting and/orreceiving) may determine its location, for example, based on the cellID, GPS information, and/or other location information, and append thelocation information to the report.

The report triggered by a WTRU may include identity information.Identity information may include the identity of the detectedout-of-coverage WTRU and/or the identity of the WTRU transmitting themessage (e.g., on the synchronization channel). The identity may includea WTRU specific ID, a ProSe ID, a ProSe Group ID, a ProSe ApplicationID, and/or the like. The report triggered may include informationrelated to one or more service (e.g., one or more service identities)for the detected out-of-coverage WTRU and/or for the WTRU transmittingthe message. This information may be used, for example, to establish arelay service.

The report may include the specific plurality of resources, sub-framesand/or duration over which it may expect to receive data and/or receivedata (e.g., as determined by control message, scheduling assignment,broadcast message, etc.)

The report triggered by a WTRU may include information relating towhether an out-of-coverage WTRU is present and/or absent. An indicationwhen the in-coverage WTRU detected an out-of-coverage WTRU requestingand/or providing PS service, an indication when the in-coverage WTRUstops detecting the out-of-coverage WTRU (e.g., using measurements),and/or an indication when the out-of-coverage WTRU stops requestingrelay service and/or when the WTRU detects a D2DSS from a neighboringWTRU, may be included in the report.

SFN (system frame number) and/or a timer reference may be used.

The report triggered by a WTRU may include information relating to thereason for triggering the transmission of the report, the request,and/or the transmission message (e.g., over a synchronization message).The reasons to trigger a report may include a request to initiate ProSediscovery and/or communication for devices that may be operating inanother frequency, detection of a neighboring WTRU to initiatecommunication with, a neighboring WTRU is no longer available, a newWTRU is detected, a change of pattern and/or configuration request, arequest to stop a ProSe service, and/or the like.

Triggers may be provided. The WTRU may trigger a report, a request for apattern, and/or the transmission of a pattern (e.g., over asynchronization message) based on the configuration. The WTRU mayinitiate the transmission when it receives L3 signaling that requeststhe WTRU to initiate a report and/or message transmission, and/or whenthe WTRU is configured for such reporting and another trigger initiatestransmission of the report. Signaling may be specific to a D2D and/orprose service (e.g., communication and/or discovery) and/or may beWTRU-specific (e.g., applicable to any identities).

Triggers for the report may be event-based. For example, the trigger maybe based on detection of a neighboring WTRU, a neighboring WTRU leaving,a request to initiate a ProSe service and/or initiate discovery, achange of pattern and/or resource allocation used by neighboring WTRU,and/or the like.

The report may be triggered when the in-coverage WTRU detects anout-of-coverage WTRU. The WTRU may detect the neighboring WTRU based ona received D2DSS, a synchronization message, and/or data received fromthe neighboring WTRU requesting a connection (e.g., solicited and/orunsolicited mode) and/or a WTRU performing PS communication with whichthe in-coverage WTRU can communicate with (e.g., the WTRUs belong to thesame group and/or is allowed to communicate according to the ProSeconfigurations). The report may be triggered when an in-coverage WTRUdetects the out-of-coverage WTRU is no longer available and/or theout-of-coverage WTRU is no longer requesting the service.

The WTRU may trigger a request and/or report when an application requestfrom a server to initiate a ProSe service is received. The requestand/or a pattern request and/or report from an in-coverage WTRU may beto enable the WTRU to detect and/or discover an out-of-coverage WTRU.The network may configure the WTRU for additional reporting, forexample, once the neighboring WTRU has been detected and/or report tothe network a request for opportunities to communicate with thediscovered WTRU. The WTRU may trigger a report when it determines that aneighboring WTRU has changed the pattern and/or the resource allocation.

Triggers may be based on measurements and/or other detected WTRUs. TheWTRU may trigger a report, a request for a pattern, and/or thetransmission of a pattern (e.g., over a synchronization message) whenconnected to a higher priority synchronization source and/or when theWTRU detects another WTRU transmitting a synchronization originatingfrom a lower priority source synch (e.g., a first WTRU is connected toan eNB and detects a second WTRU that is sending a synch signal and isconnected to another WTRU and/or another synch source). A trigger may bewhen the WTRU detects a second WTRU which is not connected to an eNB. Atrigger may be when the WTRU detects a second WTRU operating on afrequency other than its frequency of operation. A trigger may be whenthe WTRU detects a second WTRU that belongs to the same group (e.g., thesecond WTRU is allowed to communicate with the first WTRU). A triggermay be when the WTRU receives data from a second WTRU and determinesthat the WTRU is not in the coverage of the eNB (e.g., this may use anindication in the SA that the WTRU is not in coverage if there is not aD2DSS, SCI, SSS, other control signal and/or a message). A trigger maybe when the WTRU detects different transmission patterns from differentsynchronization sources.

Triggers for the report may be periodic. The WTRU may initiate reportingperiodically, for example, if (e.g., only if) there is one or more(e.g., possibly configurable number of) transmissions applicable to thereporting period. The reporting may be stopped when the WTRU detectsthat the out-of-coverage WTRU is no longer available (e.g., based onmeasurement) and/or the out-of-coverage WTRU stops requesting theservice.

Triggers for the report may be aperiodic. The WTRU may initiatereporting from the reception of control signaling that requests that theWTRU perform reporting. Signaling may be received from a network nodeand/or may be dedicated signaling and/or signaling applicable to aplurality of WTRUs (e.g., received on a broadcasting channel and/or on acommon control channel).

The WTRU may transmit the report using L2 (e.g., MAC) signaling (e.g.,as a MAC Control Element), as L3 (e.g., RRC) signaling (e.g., as a RRCPDU as part of a reporting procedure), and/or as higher layer signaling(e.g., such as NAS signaling and/or application signaling). For example,the WTRU may receive control signaling on the PDCCH (e.g., an aperiodicrequest) that may trigger such reporting. The WTRU may assemble thereport as a MAC control element and/or include it in an uplinktransmission (e.g., its next uplink transmission). The eNB may be theendpoint of the reporting procedure.

The WTRU may receive a request on a signaling radio bearer (SRB) as anRRC PDU that triggers such reporting. The WTRU may assemble the reportas a RRC PDU and/or make it available for transmission on the concernedSRB.

The WTRU may trigger reporting at the application level. For example,the WTRU may assemble an application layer control packet and/or make itavailable for transmission, for example, as a RRC PDU and make itavailable for transmission on the concerned SRB (e.g., in case NAS isused) and/or as a user plane data and make it available for transmissionfor a corresponding DRB. The ProSe and/or the application server may bethe endpoint of the reporting procedure.

The WTRU may trigger reporting. If the WTRU is in RRC IDLE mode, theWTRU may initiate a transition to CONNECTED mode and/or transmit thereport according to the applicable signaling method. The WTRU may remainin IDLE mode and/or delay the transmission of the report until it movesto CONNECTED mode, for example, if RRC and/or a higher layer protocol isused.

One or more of the following actions may be performed upon reception ofa report. The network and/or controlling node that receives a report mayanalyze the resource pool information and perform one or more of thefollowing, for example, from reports received from multiple sources. Thenetwork and/or controlling node may determine which resource it mayallow the in-coverage WTRU to communicate within the resource pool. Thenetwork and/or controlling node may initiate a procedure thatreconfigures the resources for one or more WTRUs. The network and/orcontrolling node may use this information to avoid scheduling the WTRUsin the given resources and/or time periods. For example, the eNB maydetermine a gap pattern for the in-coverage WTRU and configure the WTRUwith the gap pattern.

Upon receiving a report, the eNB may determine, provide, and/orconfigure a gap and/or time pattern for the WTRU. The gap pattern may bea bitmask and may indicate the TTIs when the WTRU may not be scheduledfor normal communications and/or the pattern may correspond to a period,cycle, and/or duration within a period (e.g., each period) the WTRU maynot be scheduled for communication with the eNB. Upon receiving areport, the eNB may analyze the requested gap pattern and if it is notdeemed efficient, the eNB may provide the WTRU with a new gap pattern.

The WTRU may use the gap pattern to switch to the out-of-coverage linkwith the neighboring WTRU. The WTRU may send the gap pattern to theout-of-coverage WTRU and/or the new gap pattern received from the eNB tothe out-of-coverage WTRU.

The eNB may remove the gap configuration, for example, when the reportincludes an indication informing the eNB that the out-of-coverage WTRUis no available and/or no longer requesting the service.

Network resource management may be provided. The network may allocate anamount of resources for D2D discovery WTRUs. If a neighbor eNB sharesthe same resources, the chance that two D2D WTRUs in proximity use thesame resource to transmit discovery signal may be high, for example,since there may be limited resources. With proper resource management bythe network, interference and/or collisions may be avoided and/ormitigated through coordination between eNBs and/or centralized controlof discovery resources. The network may manage resource management by,for example, determining which resources may be allocated, to which D2DWTRU the resources may be allocated, and/or how the WTRU determines theresources to select to transmit (e.g., to transmit a discovery signal ora D2D communication).

D2D WTRUs may select resources for transmitting a discovery signal(e.g., D2D message). The monitoring D2D WTRUs may monitor the resources(e.g., all the resources) for discovery, for example, as allocated bythe network. There may be more than one type of discovery, for example,which may be based on network allocation of resources to the WTRU. Thenetwork may allocate resources to one or more D2D WTRUs on a non-WTRUspecific manner. For example, a WTRU (e.g., each WTRU) may select theresource to transmit from a set of resources (e.g., a resource pool)allocated by network. The network may allocate resources to one or moreD2D WTRUs on a WTRU specific manner. For example, a WTRU (e.g., eachWTRU) may be scheduled with dedicated resources to transmit a discoverysignal.

The resources may be defined as a set of PRBs and/or subframes which maybe used for discovery. D2D WTRUs under the same eNB may not createinterference to each other since the network may schedule the resourcefor each WTRU without any collision (e.g., as in Type 2 D2D discovery).Without any coordination and/or central control of neighbor eNBs,collisions may occur at the border of two eNB areas. The network may nothave any knowledge about the resources used by each D2D WTRU fortransmission. Without proper allocation of resources, there may be manycollisions within the same eNB area and/or the WTRU under an eNB maycause interference to other WTRUs under neighbor eNBs.

A WTRU at cell center may refer to a WTRU that is close to the center ofthe cell to which it is associated (e.g., distance between WTRU and eNBmay be less than a threshold). A WTRU at cell edge may refer to a WTRUthat is close to the edge of the cell to which it is associated (e.g.,distance between WTRU and eNB may be greater than a threshold). The WTRUmay be associated to a cell, for example, if the cell is the WTRU'sserving cell (e.g., when the WTRU is in Connected Mode), if the cell isthe closest cell (e.g., in terms of signal strength, for exampleindicated by RSRP) to the WTRU, and/or if the cell is the cell that theWTRU camps on (e.g., in Idle Mode).

A WTRU may be configured when it is located at cell center, for example,by measuring the signal from one or more eNBs. For example, a WTRU maybe configured to determine that it is at cell center by comparing themeasured RSRP value of its associated cell to a threshold. If themeasured RSRP value is above a threshold (e.g., the signal power isabove a threshold), the WTRU may determine that it is located at or nearcell center. A WTRU may determine that it is at cell center by comparingthe measured RSRP value of its associated cell (e.g., primary cell) to ameasured RSRP value of one or more cells (e.g., cell(s) adjacent to theprimary cell). The WTRU may determine that it is located at cell center,for example, if it determines that the RSRP value of its associated cell(e.g., primary cell) is larger than a value (e.g., preconfigured value),for example, of RSRP measurements from one or more cells (e.g., adjacentcell(s)). For example, the WTRU may use hysteresis (e.g., and/or time totrigger, make measurement for a period of time, and/or the like) indetermining whether or not it is at cell center, for example, to avoidan undesirable ping-pong effect. A WTRU at cell edge may refer to a WTRUwhich is close to the edge of the cell to which it is associated.Methods similar to those described for determining whether or not a WTRUis at cell center may be used by a WTRU to determine whether or not itis at cell-edge. For example, a WTRU may determine that it is located atcell edge if it determines that the RSRP value of its associated cell issmaller than a value (e.g., preconfigured value).

A D2D WTRU may be allocated with a set of resources (e.g., resourcepool) to transmit a discovery signal. The WTRU may use one or moreresources to start transmitting. If the network fully schedules the WTRUwith the resources for transmission, then the interference caused bycollisions may be avoided through resource orthogonalization, which forexample, may mean that the WTRU may use its own dedicated resources totransmit and/or the resources may not overlapped in time and/orfrequency. If the WTRU is allocated (e.g., only allocated) with a set ofresources for transmission and/or the WTRU selects the resourcesautonomously, two or more D2D WTRUs in proximity may select the sameresource for transmission, which for example, may cause collisionsand/or interference. In this case, the network may not know that thecollisions and/or interference are occurring.

One or more of the following may be performed, for example, to minimizethe chance that two D2D WTRUs in proximity select the same resource fortransmission.

The network (e.g., an eNB) may allocate resources for one or more D2DWTRUs to select for transmission. The eNBs may share the same resourcesand/or an eNB (e.g., each eNB) may use a set of different resources, forexample, for type 1 or mode 2 (e.g., WTRU selected) resource allocation.An eNB may allocate resources (e.g., a subset of resources) based on theWTRU location and/or measurements (e.g., cell center, cell edge, etc.),resource utilization in an area, prose application priority, discoveryprocess characteristics and/or configuration, and/or the like.

FIG. 10 is a diagram of an example of resource allocation of resources(e.g., discovery) across two eNBs, eNB A and eNB B. Type 1 discovery mayrefer to when the network allocates resources to D2D WTRUs on a non-WTRUspecific manner, for example, such that a WTRU (e.g., each WTRU) mayselect the resource to transmit from a set of resources (e.g., from aresource pool) allocated by network. Type 2 discovery may refer to whenthe network allocates resources to D2D WTRUs on a WTRU specific manner,for example, such that a WTRU (e.g., each WTRU) may be scheduled withdedicated resources to transmit a discovery signal. In FIG. 10, (A) maybe used to denote a first eNB, eNB (A), and (B) may be used to denote asecond eNB, eNB (B).

Type 1 and type 2 discovery may use different sets of resources and/orthe allocation of resources for type 2 discovery may be taken from thesame resource pool as used for type 1 discovery, for example, as shownin example (a) of FIG. 10. For type 1 discovery, eNBs may share the sameset of resources for discovery signal transmission. For example, eNB (A)and eNB (B) may use resource pools 1002 for type 1 D2D transmission. Fortype 1 discovery, eNBs may allocate different sets of resources forWTRUs at the cell center and WTRUs at the cell edge, for example, asshown in the example (b) of FIG. 10. For example, eNBs A and B mayallocate the same set of resources for WTRUs in the cell center (e.g.,resource pools 1004), and a different set of resources for cell edgeWTRUs (e.g., resource pools 1006). The set of resources (e.g., resourcepools) used for cell edge WTRUs may be the same across the differenteNBs, for example as illustrated in example (b) of FIG. 10.

An eNB (e.g., each eNB, for example, eNB A and eNB B) may allocatedifferent resource sets for WTRUs at the cell center and at the celledge, for example, as shown in the example (c) of FIG. 10. For example,different eNBs (e.g., eNB A and eNB B) may share the same set ofresources for the cell center WTRUs. Different eNBs (e.g., eNB A and eNBB) may allocate different resource sets for cell edge WTRUs. Forexample, eNBs (A) and (B) may use resource pools 1008 at their cellcenters. eNB (A) may use resource pools 1010 at its cell edge. eNB (B)may use resource pools 1012 at its cell edge. eNB (A) and eNB (B) mayuse different resource at their cell edges, for example to avoidinterference.

eNB (A) and eNB (B) may use the same resource pools 1002 for type 1communication, for example as shown in example (d) of FIG. 10. eNB (A)and eNB (B) may use different resource pools for type 2 communication.For example, eNB (A) may use resource pools 1014 and eNB (B) may useresource pools 1016 for type 2 communication, as exemplified in examples(a), (b) and (c) of FIG. 10. eNB (A) and eNB (B) may use the sameresource pools 1018 for type 2 communication, as illustrated in example(d) of FIG. 10.

The eNB may allocate a different set of resources for differentapplication priorities. For example, a different set may be availablefor WTRUs transmitting a signal from a higher priority applicationand/or another set of resources may be available for transmission from alower priority application. The priority of the applications may beconfigured by the network, a ProSe server, and/or may be preconfigured.The discovery process characteristics may be configured by the network,the ProSe server, and/or may be preconfigured. Discovery processcharacteristics may refer to, for example, the type of discoveryprocess, the type of application (e.g., public safety or commercial),the type of method (e.g., open/restricted discovery), the type of QoScharacteristics, latency of transmission, rate of transmissions ormessage generation, and/or the like.

An eNB may achieve resource coordination. To allow the network toallocate different sets of resources to D2D WTRUs, coordination acrossdifferent eNBs may be provided and/or a centralized coordinator may bein charge of the resource management between different eNBs.

Inter-eNB coordination of resources may be provided. The different eNBsmay exchange the sets of resources allocated to D2D WTRUs, for example,via the X2 interface. For example, one eNB may send an X2 signal to aneighbor eNB(s), which may indicate a set of resources allocated for itsD2D WTRUs (e.g., resources at the cell center and/or resources for D2DWTRUs at the cell edge). The neighbor eNB(s) may allocate resource setsto its D2D WTRUs based on this information. For example, the neighboreNB(s) may share the same set of resources for D2D WTRUs at cell center,and/or may use different sets of resources for WTRUs at cell edge, forexample, as shown in the example (c) of FIG. 10.

Different eNBs may exchange the resource information, for example, ifthe sets of resources allocated remain the same during a period. If theeNB changes the resources allocated to WTRUs, the eNB may send suchinformation to its neighbor eNBs. Neighbor eNBs may adjust the resourcesto allocate, for example, when an eNB receives a report from the WTRUand/or determines that more resources will be allocated. The eNB mayinform the neighbor eNBs of such changes.

Centralized resource management may be provided. Neighbor eNBs in onearea may be connected to a central node. The centralized node maycontrol the resource management among one or more neighbor eNBs. Thecentralized node may allocate an eNB with the proper sets of resources(e.g., a plurality of resource pools). For example, the centralized nodemay allocate adjacent eNBs with the same set of resources for the D2DWTRUs at the cell center and different sets of resources for D2D WTRUsat the cell edge, for example, as shown in the example (c) of FIG. 10.

eNB A and eNB B may be assigned a first resource pool 1008 to use at ornear the center of their respective cells, for example, as illustratedin example (c) of FIG. 10. The eNB A and eNB B may use the firstresource pool 1008 concurrently at their cell centers without causingsignificant interference because a distance between the cell centers maybe greater than a threshold distance in which reuse causes interference.eNB A and eNB B may be assigned different resource pools to use at ornear their cells edges, for example, as illustrated in example (c) ofFIG. 10. For example, eNB A may be assigned a second resource pool 1010and eNB B may be assigned a third resource pool 1012. eNB A and eNB Bmay not use the same resource pool at their cell edges because theircell edges may overlap or a distance between their cell edges may beless than a threshold distance in which reuse causes interference.

One or more WTRUs may select a set of resources (e.g., a resource pool)to use for D2D communication (e.g., transmission or reception). A WTRUbeing served by eNB A may select a resource pool from a plurality ofresource pools to send information using D2D communication, for example,as illustrated in example (c) of FIG. 10. A WTRU being served by eNB Amay select the first resource pool 1008, for example when the WTRU is ator near the center of the cell being served by eNB A. A WTRU beingserved by eNB A may select the second resource pool 1010, for examplewhen the WTRU is at or near the edge of the cell being served by eNB A.A WTRU being served by eNB B may select the first resource pool 1008,for example when the WTRU is at or near the center of the cell beingserved by eNB B. An example of this is illustrated in example (c) ofFIG. 10. A WTRU being served by eNB B may select the third resource pool1012, for example when the WTRU is at or near the edge of the cell beingserved by eNB B.

The set of resources to be used by a WTRU for transmission may beautonomously determined by the WTRU and/or explicitly configured by thenetwork, for example, based on one or more criteria. The resource setselection criteria may be a function of one or more of the followingmeasurements and/or criteria determined by the transmitting WTRU.

The resource selection (e.g., resource pool selection) may be based onRSRP measurement(s). The RSRP measurement of the serving cell, the eNBin which the WTRU is camped in idle mode, and/or the RSRP from aneighboring eNB may be used for resource selection. For example, a WTRUbeing served by eNB A may determine a RSRP measurement and select aresource pool from a plurality of resource pools based on the RSRPmeasurement.

A WTRU may determine a RSRP measurement of the serving cell. The WTRUmay compare the measured RSRP of the serving eNB to a threshold (e.g.,preconfigured threshold). For example, if the measured RSRP is largerthan a threshold, the WTRU may select from the set of the correspondingresources (e.g., resources configured for WTRUs that have an RSRP largerthan a threshold). If the measured RSRP is less than the threshold, theWTRU may select from the other set of resources that are for WTRUs withRSRP smaller than the threshold. For example, a WTRU being served by eNBA may determine a RSRP measurement of a cell being served by the eNB A.The WTRU may select the first resource pool 1008, for example when theRSRP measurement is greater than a threshold. The WTRU may select thesecond resource pool 1010, for example when the RSRP measurement is lessthan the threshold.

A WTRU may use a RSRP measurement from a neighboring eNB to select aresource pool. For example, a WTRU being served by eNB A may use a RSRPmeasurement of a cell that is being served by eNB B (e.g., a neighboringcell, for example an adjacent cell). The WTRU may determine that it isproximate to a neighboring cell when the RSRP measurement of theneighboring cell is above a threshold. A WTRU being served by eNB A mayselect the second resource pool 1010, for example when the RSRPmeasurement of a neighboring cell (e.g., a cell being served by aneighboring eNB, eNB B) is above a threshold. The WTRU may determinethat it is distal from a neighboring cell when the RSRP measurement ofthe neighboring cell is below a threshold. A WTRU being served by eNB Amay select the first resource pool 1008, for example when the RSRPmeasurement of a neighboring cell (e.g., cell being served by eNB B) isbelow a threshold.

Different resource sets (e.g., resource pools) may be configured to beused for different RSRP ranges. For example, the first resource pool1008 may be associated with a first range of RSRP values and the secondresource pool 1010 may be associated with a second range of RSRP values.The first range of RSRP values may include RSRP values above a thresholdand the second range of RSRP values may include RSRP values below thethreshold. A WTRU may select the first resource pool 1008, for examplewhen the RSRP measurement is within the first range of RSRP values. TheWTRU may select the second resource pool 1010, for example when the RSRPmeasurement is within the second range of RSRP values. A range of RSRPvalues may include a low RSRP threshold that indicates a lower limit ofthe range and a high RSRP threshold that indicates a higher limit of therange. A WTRU may determine that a RSRP measurement is within the rangeof RSRP values when the RSRP measurement is between the low RSRPthreshold and the high RSRP threshold (e.g., greater than the low RSRPthreshold and less than the high RSRP threshold). A range of RSRP valuesmay be open-ended. For example, a RSRP range may have one (e.g., onlyone) limit, (e.g., only a lower limit or only a higher limit). A RSRPthreshold may be a low RSRP threshold of an open-ended range of RSRPvalues or a high RSRP threshold of the open-ended range of RSRP values.

The WTRU may report the measurements (e.g., a RSRP measurement) based ona triggering criteria to the serving eNB (e.g., eNB A). The eNB mayconfigure and/or indicate the WTRU with the set of resources. Forexample, the eNB may indicate to the WTRU that the first resource pool1008 is associated with a first range of RSRP values and the secondresource pool 1010 is associated with a second range of RSRP values. TheeNB may indicate the resource pool(s), RSRP range(s) and/or RSRPthreshold(s) via radio resource control (RRC) signaling. For example,the eNB may send a configuration to the WTRU. The configuration mayidentify the resource pool(s), RSRP range(s) and/or RSRP threshold(s).

The WTRU may compare RSRP from its serving eNB and/or one or moreneighbor eNBs. For example, a WTRU being served by eNB A may compareRSRP measurements of the cells being served by eNB A and eNB B. Thenetwork may configure two or more sets of resources for D2D WTRUs in thecenter of eNB area and in the edge of the eNB area. For example, eNB Amay determine that the first resource pool 1008 be used at or near cellcenter and the second resource pool 1010 be used at or near cell edge.

The WTRU may determine which set of resources (e.g., which resource poolto select from a plurality of resource pools) to select as a function ofthe RSRP of the serving eNB and/or one or more neighboring eNBs. Forexample, a WTRU being served by eNB A may select one of the firstresource pool 1008 or the second resource pool 1010 based on a RSRPmeasurement. For example, the WTRU may select resource pool 1010 (e.g.,the resources for cell center) when the measured RSRP of the serving eNB(e.g., eNB A) is larger than the RSRP of one or more neighboring eNBs(e.g., eNB B), for example, by a certain value and/or for a period oftime. For example, the WTRU may select the first resource pool 1008 whena difference between the measured RSRPs of eNB A and eNB B exceeds athreshold. Otherwise, the WTRU may select from the other set ofresources (e.g., second resource pool 1010). For example, the WTRU mayselect the second resource pool 1010 when the difference between themeasured RSRPs of eNB A and eNB B is below a threshold.

The WTRU may report the criteria to the serving eNB (e.g., eNB A). Forexample, the WTRU may send a RSRP measurement to eNB A. The eNB mayconfigure the WTRU with the set of resources to select. For example, theeNB A may configure the WTRU to select a resource pool by sending aconfiguration to the WTRU. The configuration may indicate a resourcepool that the WTRU may use based on the RSRP measurement. For example,WTRU may report ‘1’ if the RSRP from the serving eNB (e.g., eNB A) islarger than that from one or more neighbor eNBs (e.g., eNB B), forexample, by a value and/or for a period of time, and the WTRU may report‘0’ otherwise. An eNB (e.g., eNB A) may configure a WTRU to select acell center resource pool (e.g., first resource pool 1008) when the WTRUreports ‘1’. An eNB (e.g., eNB B) may configure a WTRU to select a celledge resource pool (e.g., second resource pool 1010) when the WTRUreports ‘0’.

The resource selection may be based on the path loss to the serving eNBand/or to one or more of the neighboring eNBs. The WTRU may compare themeasured path loss to the serving eNB to a threshold (e.g., a predefinedthreshold), for example, similar to RSRP measurements. The WTRU mayselect the set of resources to choose from based on the comparisonresult and/or the WTRU may compare the path loss to the serving eNBand/or one or more neighbor eNBs. The WTRU may select from the set ofresources for cell center WTRUs (e.g., first resource pool 1002) if thepath loss to serving eNB (e.g., eNB A) is less than that to one or moreneighbor eNBs (e.g., eNB B). Otherwise, the WTRU may select from the setof resources for cell edge WTRUs (e.g., second resource pool 1010). TheWTRU may report the measurement to the eNB based on a triggeringcriteria. The eNB may configure the resource set to use.

The resource selection may be based on the timing advance value to theserving eNB and/or to the neighboring eNBs. For WTRUs in connected mode,the timing advance value to its serving eNB and/or one or more neighboreNBs may be used as a criteria to select the resource set. For example,if the timing advance value in the serving eNB is less than a threshold,the WTRU may select the corresponding configured resource (e.g., whenthe given criteria is met). Otherwise, the WTRU may select from anotherset of resources. The WTRU may report to the eNB based on the comparisonresults of one or more timing advance values.

The resource selection may be based on the measured energy level on oneor more (e.g., a sub-set) of allowed discovery resources. The WTRU maydetermine the set of resources to select from and/or may report to theeNB based on the measured resource utilization on one or more (e.g., asubset) of discovery resources. Resource utilization may be determined,for example, by measuring the amount of energy and/or by monitoringcontrol signaling and/or discovery signaling in the resources ofinterest, for example, as described herein.

The WTRU may perform measurements (e.g., energy level on the resourceswithin a set) on one or more sets of resources and use the results ofthe measurements to determine which resource set to use. The WTRU mayselect the resource set in which the measured resource utilization isthe lowest (e.g., the lowest energy level was detected across theresources (e.g., all resources) in the set over one measurement and/orover a number of measurements). Resource selection (e.g., initialresource selection) may be performed based on such measurements and/orthe WTRU may randomly select a resource across the available resourcesets (e.g., from a plurality of resources in a resource pool). Resourceselection (e.g., initial resource selection) may be based on a networkconfigured priority order and/or based on other measurements, forexample, as described herein. Once a resource selection (e.g., aninitial resource selection) is performed, the WTRU may change a resourceset, for example, if the measured energy level across resources (e.g.,all the resources) is higher than a threshold, for example, for a periodof time. The WTRU may select a resource set (e.g., a new resource set)based on the measured energy in another set of resource. For example,the WTRU may select the resource set with the lowest energy level, theWTRU may randomly select a resource set, and/or the WTRU may select thenext highest priority set of resources. The WTRU may select a set ofresources if another set of resources has a lower average resourceutilization across its resources, for example, by a threshold and/or fora period of time. If the resources are occupied on one or more (e.g.,all) resource sets, the WTRU may send a report to the network.

The resource selection may depend on the priority of the application.The WTRU may be configured with a priority (e.g., a Prose applicationpriority). One or more resource sets may be configured with one or moreassociated application priority classes. The WTRU may determine whichresource set to use based on the priority of the application for which adiscovery signal is being transmitted. The WTRU may select the resourceswith the highest available priority that are equal to or lower than theconfigured application priority.

The resource selection may depend on one or a combination of theconfigured characteristics of a ProSe application (e.g., for discoveryand/or for communication). For example, resource selection may depend onthe type of application, use of application, public safety orcommercial, QoS characteristics (e.g., latency, rate, etc.), powercharacteristics/requirements, type of discovery (e.g., open/restricted)or Model A vs. Mode B discovery, type of communication (e.g., unicast,multicast, or groupcast), etc.

The resource selection for communication may be performed to select oneamongst the multiple configured SA resource pools or data transmissionpools.

The WTRU may be configured with one or a combination of characteristics.Each resource pool may be configured with one or a combination ofcharacteristics. The WTRU may select a resource set or a set ofresources that are configured with the same characteristic as the ProSeapplication in the WTRU. For example, if the WTRU is configured with apublic safety type of application, the WTRU may select the set ofresources that are configured for public safety.

The WTRU may select a resource set that meets the power classrequirement and/or characteristic of the given application or set ofapplications. The WTRU may select a resource set from the availableresources that is configured with the type of discovery associated tothe given application. The WTRU may select from a resource set thatallows the WTRU to meet one or more of the QoS criteria, including forexample, latency and/or rates. From the configured set of resource, theWTRU may determine the resource set that has the periodicity and/ornumber of D2D available subframes for D2D transmissions that would allowthe WTRU to meet the requirements and/or rates.

The WTRU may select from a resource set that allows the WTRU to meet oneor more QoS criteria, including for example, a guaranteed bit rate. Forexample, the WTRU may determine the resource set that is configured tosupport a configured PBR or GBR of the logical channel assigned to theD2D transmission packet.

Triggers to perform selection of resources (e.g., autonomous selectionof resources) and/or to initiate a report to the eNB may be provided.The WTRU may perform resource selection and/or reporting to the networkwhen a discovery and/or communication process is initiated (e.g., thefirst time when WTRU attempts to select resources to transmit discoverysignal), for example, when the WTRU determines to transmit a discoverysignal or message for the first time. The WTRU may report the criteriathe WTRU has to meet and/or the characteristics of the eNB to the eNBbased on the measured results, for example, as described herein.

At the beginning of a (e.g., each) discovery occasion, the WTRU mayperform a measurement (e.g., RSRP measurement) and/or use themeasurement to select the appropriate resource set (e.g., resourcepool). The WTRU may utilize resources from this resource set for theduration of the discovery process and/or for a configured time period.

The WTRU may perform resource selection (e.g., dynamic resourcesselection) according to one or more of the criteria defined herein, forexample, at every transmission. The WTRU may monitor the resource setand/or measurements. If one or more of the conditions described hereinare met, the WTRU may change the resource set it uses. The WTRU maytrigger a report to the network when the conditions described herein aremet, for example, when WTRU measured RSRP of its serving eNB is abovethe threshold (e.g., for a duration of time) and/or is decreasing as itmoves further from the eNB. If the RSRP value drops to under thethreshold, the WTRU may send a report to the eNB indicating such changesand/or may change (e.g., autonomously change) the set of used resources.

The WTRU may perform resource selection and/or reporting to the networkwhen the WTRU is configured by the network to send such report, forexample, which may be used for the network to decide which set ofresources and what characteristics may be allocated to the WTRU.

The WTRU may perform resource selection and/or reporting to the networkwhen the WTRU cannot find an available set of resources to select. Forexample, if all sets of resources are occupied based on the measuredenergy level. The WTRU may select a resource set, may be randomlyperformed across available resource sets, and/or based on a networkconfigured priority order. If the resource set is selected based on anetwork configured priority order, the network may broadcast a tableindicating the priority order of one or more of the resource sets.

Resources may be selected when the application and/or discovery processmeets different criteria. A set of resources (e.g., a discovery resourcepool, a SA transmission pool for communication, a communication datatransmission pool, etc.) may be configured with an index thatcorresponds to one or a combination of the different criteria that theWTRU is allowed to select from. For example, an explicit mapping betweenan index and a criteria or combination of criteria may be defined. TheWTRU may determine the associated index depending on its configuredcriteria (e.g., type of application, power range, QoS, priority, bitrate, etc.).

Table 1 is a table that illustrates an example mapping of a three bitindex and associated criteria. The set of criteria that define theresource usage may correspond to the type of application and/or powerrange for which the resource set can be used. A mapping table may beproduced for different resource usage definition that combine differentset of desirable criteria and/or with a different number of bits for theindex number. For example, more bits can be used if the prioritycriteria is included in the definition of the resource usage.

TABLE 1 Example Mapping of a Three Bit Index and Associated CriteriaIndex number Description of resource usage 000 Resource set can be usedby WTRUs that have a commercial applications 001 Commercial applicationand low power range 010 Commercial application medium power range 011Commercial application and high power range 100 Resource set can used byWTRUs configured or that are transmitting public safety application type101 PS and low power range 110 PS and medium power range 111 PS and highpower range

The discovery process and/or communication session may be independentlyconfigured with the different criteria. The WTRU may determine to whichindex the set of criteria maps. The WTRU may select the resource setassociated to that index. The WTRU may be explicitly configured with anindex. If no resources are configured with the given index, the WTRU maydetermine the next resource set that meets the configured criteria thebest.

A discovery process and/or communication session may be associated withmore than one desired usage index (e.g., in a priority order). The WTRUmay be configured to match the offered usage index to one or more of thedesired usage index (e.g., in order of priority). If that does not work,the WTRU may revert to a default resource and/or a resource that isconfigured for any type of service.

The resource set may be configured with a resource index and with ameasurement criteria (e.g., RSRP threshold associated with resource).Each criteria may be independently configured. Priority amongst thecriteria may be established

A resource set may be configured (e.g., explicitly and/or independentlyconfigured) with one or more different criteria. For example, a resourceset may indicate whether it is for public safety (PS) use, commercialuse, or neither (e.g., resources may be for any application type). In anexample criteria, a resource set may be configured with a power range(e.g., low, medium, high, or none). None may imply that all theresources may be used for all power ranges. For example, a resource setmay indicate the type of QoS it supports, the packet bit rate (e.g., PBRor GBR) it can support, and/or the like.

The WTRU may select the first resource set(s) associated with a firstcriteria (e.g., highest priority criteria). The WTRU may use the nextcriteria, determined based on the order of priority, to select the nextset of resources within the first resource set and so on. For example,the WTRU may first select the set of resources associated for use withan application type (e.g., PS or commercial). The WTRU may selectresources that meet a set of power range criteria. The WTRU may selectthe set of resources according to the RSRP measurement and/or resourceconfiguration.

The WTRU may select the set of resources associated with a configuredpriority level. The WTRU may select the resource sets with the highestpriority level that is equal to or lower than the WTRU configuredapplication priority level. The priority level may be a lower prioritythan the resources allowed to be used according to the RSRP measurement.So the WTRU may select the set(s) of available resources that meet theconfigured RRSP measurement criteria and then select the resource withthe higher priority level that is equal to or lower than the applicationpriority.

If the WTRU is unable to find a resource set with offered usage indexthat matches the usage index of a given discovery process and/orcommunication session, the WTRU may be configured with guidelines onusing a closest match resource set. For example, if the WTRU is unableto find a resource set for short range discovery, the WTRU may beconfigured to use resources from a medium range resource set whilerespecting its maximum power transmission requirement. For example, theWTRU may have rules to select the resource set configured with a packetbit rate equal to or higher than the packet bit rate of the radio bearer(e.g., logical channel) of the transmission packet.

A default pool may be configured that may be used for discovery messageswith any required usage index requirements. The WTRU may select thedefault pool when no other match is found.

WTRU-autonomous resource control may be provided. The transmitting WTRUmay determine how many discovery transmissions (e.g., including 0) toperform in a given discovery occasion and/or time period. By configuringthe WTRU discovery transmission rate, the network and/or system mayadjust the amount of interference and/or the service quality.

The WTRU may be configured with a fixed discovery transmission rate. Forexample, the WTRU may be configured by the network with a givendiscovery transmission rate. The WTRU may receive the configuration viadedicated signaling (e.g., via RRC, NAS, from the ProSE server, and/orthe like). The WTRU may receive the configuration via the broadcastchannel (e.g., via one or more SIBs). The configuration may identify theresource pool(s), RSRP range(s) and/or RSRP threshold(s).

The WTRU may be configured with a discovery transmission rate, forexample, which may be parameterized using one or more of the following.The WTRU may be configured with an average rate expressed in a number ofdiscovery transmissions per seconds. The WTRU may determine how manydiscovery transmissions to perform in one or more (e.g., a series of)discovery occasions to achieve the rate. The WTRU may be configured totransmit the discovery signals at regular intervals to achieve the rate.The WTRU may be configured with a number of discovery transmissions fora specific number of discovery occasions and/or specific time interval.For example, the WTRU may be configured to transmit N transmit discoverysignals over N discovery occasions. The WTRU may be configured totransmit N transmit discovery signal during a time interval, forexample, which may be specified in a number of frames (e.g., Nframes)and/or absolute time (e.g., seconds).

The WTRU may be configured to repeat the discovery signal payload duringa discovery occasion, for example, when the rate permits. This mayhappen, for example, when the rate is such that the WTRU may transmitmore than one discovery signal in one discovery occasion.

The configured discovery transmission rate may be applicable to one ormore (e.g., all) discovery processes. The WTRU may be configured with adiscovery transmission rate specific to a (e.g., each) discoveryprocess.

The WTRU may determine the discovery transmission rate autonomously. TheWTRU may base its discovery transmission rate on measurements ofdiscovery resources. The WTRU may be configured with a minimum discoverytransmission rate and/or a maximum transmission rate. The WTRU may beconfigured to measure the resource utilization and update the currenttransmission rate (e.g., current_discovery_rate) after a givenmeasurement period.

The WTRU may initialize the current_discovery_rate to a value (e.g.,predefined value). The WTRU may initializes the current_discovery_rateto the minimum discovery transmission rate configured. The WTRU mayreset, re-initialize, and/or set to zero the current_discovery_rate, forexample, when one or more of the following occurs. The WTRU may reset,re-initialize, and/or set to zero the current_discovery_rate when theWTRU has not transmitted a discovery signal for a configured duration oftime. The WTRU may reset, re-initialize, and/or set to zero thecurrent_discovery_rate when the WTRU receives a signal from the network.For example, the signal may be a signal indicating a change of resourcesfor discovery (e.g., in which case the WTRU may re-initialize thecurrent_discovery_rate) and/or a signal indicating the WTRU to set itscurrent_discovery_rate to 0 (e.g., for a predefined amount of time afterwhich the WTRU may be configured to re-initialize thecurrent_discovery_rate). The WTRU may reset, re-initialize, and/or setto zero the current_discovery_rate when the WTRU determines (e.g.,measures) that the discovery resources utilization level is above and/orbelow a threshold, for example, for a configured amount of time.

There may be one or more triggers for the WTRU to increase and/ordecrease the current_discovery_rate. The WTRU may increase the value ofthe current_discovery_rate by an amount when the WTRU determines thatthe resource utilization is below a threshold, for example, for a periodof time.

The WTRU may increase the discovery transmission rate by an amount(e.g., the WTRU may double the discovery transmission rate). The WTRUmay be configured to not exceed the maximum rate configured.

The WTRU may decrease the discovery transmission rate by an amount. Forexample, the WTRU may decrease the discovery transmission rate by anamount once for a period of time (e.g., every period of time) duringwhich the WTRU determines that the resource utilization is above and/orbelow a threshold, for example, for a period of time. The WTRU maydecrease the discovery transmission rate by an amount based on theactivity state associated to one or more of its discovery processes, forexample, when the WTRU determines that it has not performed a discoverytransmission during an amount of time. The WTRU may decrease thediscovery transmission rate by an amount based on network signaling. Forexample, the WTRU may decrease the discovery transmission rate by anamount when the WTRU receives network signaling via dedicated signaling(e.g., using a DCI on (e)PDCCH masked by C-RNTI, by another configuredRNTI, by L2 MAC signaling using a MAC Control Element, and/or the like).For example, the WTRU may decrease the discovery transmission rate by anamount when the WTRU may receive network signaling via the broadcastchannel (e.g., via one or more the SIBs).

The WTRU may halve the discovery transmission rate. The WTRU may notdecrease the rate below the minimum value configured.

The WTRU may determine the discovery resource usage based on the energylevel on discovery resources. For example, the WTRU may measure theenergy level on the discovery resources (e.g., when not transmitting)and compare it to a threshold. The WTRU may determine the discoveryresource usage based on the number of successful discoveries. Forexample, the WTRU may count the number of successful discoveries andcompare it to a threshold. The WTRU may determine the discovery resourceusage based on one or more SIBs. For example, the WTRU may monitor oneor more SIBs for indication of resource utilization. The WTRU may readthe resource utilization from the one or more SIBs.

The WTRU may determine the resource utilization based on an indicationby the network, for example, signaled via one or more SIBs. For example,the WTRU may monitor the one or more SIBs for a discovery signalresource utilization overload indicator. The WTRU may increase and/ordecrease its discovery transmission rate (e.g., as described herein),for example, based on the value of the overload indicator.

The WTRU may determine that one or more discovery resources arededicated (e.g., associated to different discovery processes by thenetwork) while one or more discovery resources are shared. The WTRU mayconsider (e.g., only consider) the one or more discovery resources thatare shared in its determination of resource usage level. The WTRU mayapply the resulting transmission rate to processes associated withshared resources (e.g., only to processes associated with sharedresources).

Interference mitigation via resource randomization may be provided. Thetransmitting WTRU may select the actual transmission occasions, forexample, from a set of allowed discovery occasions, for example, torandomize the system interference.

WTRU may randomly select a resource (e.g., the set of subframes) overwhich to attempt D2D communication (e.g., discovery transmission). Thetransmitting WTRU may determine the set of subframes over which adiscovery signal may be transmitted. The WTRU may determine the numberof subframes used for discovery signal transmission (e.g., Nreq) over anumber of discovery subframes (e.g., Ndisc), for example, defined over aperiod of time (e.g., over a discovery occasion cycle) based on itsconfiguration, for example, based on one or more of the following.

The WTRU may determine the number of subframes used for discovery signaltransmission based on the number of discovery processes configured, theQoS and/or discovery transmission rate of a (e.g., each) discoveryprocess, the maximum and/or minimum discovery transmission rateconfigured and/or allowed per transmitting WTRU, and/or the minimumnumber of subframes used by the WTRU to meet its required QoS across theconfigured discovery processes.

The WTRU may select (e.g., randomly) Nreq subframes (e.g., a resource)over the total number of subframes (e.g., from a plurality ofresources), for example, during a period (e.g., Ndisc subframes), forexample to perform and/or attempt D2D communication (e.g., discoverytransmission).

The WTRU may select the resource (e.g., subframe(s), PRB(s), etc.) usinga (e.g., predefined) randomization function, for example, which may beinitialized by a WTRU-specific value. This may ensure that no two WTRUsselect the same set of resources over time. The WTRU may be configuredwith a pseudo-random sequence function initialized with a seed based ona WTRU-specific value signaled by the network and/or based on a WTRU-IDand/or part of a WTRU-ID (e.g., IMSI, T-IMSI, C-RNTI, IMEI, etc.).

The WTRU may re-initialize the randomization function at a regularinterval, for example, every time the SFN wraps around and/or at anothertime instant.

Time delay restrictions may be provided. For example, the WTRU may beconfigured with a minimum delay and/or number of subframe between twoallowed discovery transmissions. This may be used to exploit timediversity of the channel. When selecting (e.g., randomly) Nreq subframes(e.g., a resource) over the total number of subframes (e.g., from aplurality of resources) during a period (e.g., Ndisc subframes) toperform and/or attempt discovery transmission, the WTRU may ensure thatno two selected subframes violate the minimum delay requirement. Thismay be performed, for example, by discarding invalid configurations whenthey occur and/or re-attempting selection until it meets therequirements.

The WTRU may selects one or more (e.g., a set) of subframes over whichto attempt discovery transmission, for example, based on predefinedhopping pattern. The WTRU may be preconfigured with one or more set ofsubframe hopping patterns. A (e.g., each) hopping pattern may define aset of subframes over which the transmitting WTRU may transmit adiscovery signal, for example, over a period of time (e.g. over adiscovery occasion cycle).

The WTRU may determine the number of subframes used for a discoverysignal transmission (e.g., Nreq) over a number of discovery subframes(e.g., Ndisc), for example, as described herein. The WTRU may select thefamily of hopping pattern for which the hopping pattern (e.g., everyhopping pattern) allows for Nreq discovery subframes transmission, forexample, based on the value of Nreq. The WTRU may select one or more ofthe hopping patterns from that family, for example, based on a randomfunction. For example, the WTRU may select the hopping pattern using anindex generated by a pseudo-random function. The pseudo-random functionmay be initialized with a seed derived, for example, as describedherein.

Although features and elements are described with reference to LTE(e.g., LTE-A) and LTE terminology, the features and elements describedherein may be application to other wired and wireless communicationprotocols, for example, HSPA, HSPA+, WCDMA, CDMA2000, GSM, WLAN, and/orthe like.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, WTRU, terminal, base station, RNC, or any host computer.

What is claimed is:
 1. A wireless transmit receive unit (WTRU)comprising: a processor configured to: determine to send informationusing a device-to-device transmission; determine a reference signalreceive power (RSRP) measurement of a cell associated with the WTRU;select a resource pool from a plurality of resource pools based on theRSRP measurement of the cell, wherein each resource pool of theplurality of resource pools is associated with a low RSRP threshold anda high RSRP threshold, and wherein the RSRP measurement of the cell isbetween the low RSRP threshold and the high RSRP threshold of theselected resource pool; and send the information using the selectedresource pool.
 2. The WTRU of claim 1, wherein the processor is furtherconfigured to select a resource from a plurality of resources of theselected resource pool.
 3. The WTRU of claim 2, wherein the processor isconfigured to select the resource using a randomization function or apseudo-random function.
 4. The WTRU of claim 2, wherein the processorconfigured to send the information using the selected resource poolcomprises the processor being configured to send the information usingthe selected resource.
 5. The WTRU of claim 2, wherein the selectedresource comprises one or more subframes.
 6. The WTRU of claim 2,wherein the selected resource comprises one or more physical resourceblocks (PRBs).
 7. The WTRU of claim 1, wherein the processor is furtherconfigured to: receive a configuration via radio resource control (RRC)signaling; and determine, based on the configuration, that the selectionof the resource pool is based on RSRP.
 8. The WTRU of claim 7, whereinthe configuration identifies the resource pool and the range of RSRPvalues associated with the resource pool.
 9. A method comprising:determining to send information using a device-to-device transmission;determining a RSRP measurement of a cell associated with the WTRU;selecting a resource pool from the plurality of resource pools based onthe RSRP measurement of the cell, wherein each resource pool isassociated with a low RSRP threshold and a high RSRP threshold, andwherein the RSRP measurement of the cell is within the range of RSRPvalues associated with the selected resource pool between the low RSRPthreshold and the high RSRP threshold of the selected resource pool; andsending the information using the selected resource pool.
 10. The methodof claim 9, further comprising selecting a resource from a plurality ofresources in the selected resource pool.
 11. The method of claim 10,wherein selecting the resource comprises selecting the resource using arandomization function or a pseudo-random function.
 12. The method ofclaim 10, wherein sending the information using the selected resourcepool comprises sending the information using the selected resource. 13.The method of claim 9, further comprising determining that thedevice-to-device transmission is a Type 1 device-to-device transmission,the Type 1 device-to-device transmission being characterized by the WTRUselecting the resource pool from the plurality of resource pools. 14.The method of claim 9, wherein the determining to send the informationusing the device-to-device transmission comprises receiving a request tosend the information using the device-to-device transmission.
 15. Awireless transmit receive unit (WTRU) comprising: a processor configuredto: receive a device-to-device transmission request to send information;determine that resource selection is based on reference signal receivepower (RSRP); receive a RSRP threshold associated with a resource poolout of a plurality of resource pools; determine a RSRP measurement;compare the RSRP measurement with the RSRP threshold associated with theresource pool; select the resource pool to send the information viadevice-to-device transmission in response to the RSRP measurement beingabove the RSRP threshold; and send the information using the resourcepool in response to the resource pool being selected to send theinformation.
 16. The WTRU of claim 15, wherein the resource poolcomprises a plurality of resources and wherein the processor is furtherconfigured to: select a resource from the plurality of resources basedon a randomization function; and send the information using the selectedresource.
 17. The WTRU of claim 16, wherein the resource comprises asubframe or a physical resource block (PRB).
 18. The WTRU of claim 15,wherein the processor is further configured to receive a systeminformation block (SIB) that identifies the resource pool and indicatesthe RSRP threshold associated with the resource pool.
 19. The WTRU ofclaim 15, wherein the RSRP threshold comprises a low RSRP threshold ofan open-ended range of RSRP values or a high RSRP threshold of theopen-ended range of RSRP values.